GEOCHEMICAL EVALUATION OF OILS AND SOURCE ROCKS AND OIL-SOURCE ROCK CORRELATIONS, SUB-ANDEAN BASINS, PERU

Transcription

1 GEOCHEMICAL EVALUATION OF OILS AND SOURCE ROCKS AND OIL-SOURCE ROCK CORRELATIONS, SUB-ANDEAN BASINS, PERU Volume 1 Final Report Interpretation and Synthesis Prepared by: Core Laboratories, Inc Prepared for: Idemitsu Oil & Gas Company, Ltd. Core Lab Job No May 1999

2 GEOCHEMICAL EVALUATION OF OILS AND SOURCE ROCKS, AND OIL-SOURCE ROCK CORRELATIONS, SUB-ANDEAN BASINS, PERU TABLE OF CONTENTS Page No. EXECUTIVE SUMMARY Chapter INTRODUCTION Objectives Analytical Program Outline Presentation of Results Chapter 2 CHARACTERIZATION OF OILS AND CONDENSATES INTRODUCTION GENETIC OIL FAMILY A Organic Facies Thermal Maturity GENETIC OIL FAMILY B Organic Facies Thermal Maturity GENETIC OIL FAMILY C Organic Facies Thermal Maturity GENETIC OIL FAMILY D Organic Facies Thermal Maturity

3 TABLE OF CONTENTS, continued Page No. GENETIC OIL FAMILY D Organic Facies Thermal Maturity GENETIC OIL FAMILY E Organic Facies Thermal Maturity GENETIC OIL FAMILY E Organic Facies Thermal Maturity COMPARISON AMONG THE GENETIC OIL FAMILIES SUMMARY Chapter 3 SOURCE ROCK EXTRACT CHARACTERIZATION INTRODUCTION Cretaceous Source Rocks Jurassic Source Rocks Paleozoic Source Rocks Permian Carboniferous Devonian Chapter 4 OIL-SOURCE ROCK CORRELATIONS INTRODUCTION...4 1

4 TABLE OF CONTENTS, continued Page No. Oil Families Related to Cretaceous Source Rocks Oil Families Related to Jurassic Source Rocks Oil Families Related to Paleozoic Source Rocks SUMMARY CONCLUSIONS AND RECOMMENDATIONS REFERENCES APPENDIX List of Tables Table 2-1. Oil Analytical Program Table 2-2. Oil Compositional Data Table 2-3. n-paraffin and Isoprenoid Distribution Table 2-4 Saturate Biomarker Ratios Table 2-5. Aromatic Biomarker Ratios Table 2-6. Individual Component Stable Carbon Isotope Data Table 2-7. Distinguishing Geochemical Characteristics of Genetic Oil Families Table 3-1 Source Rock Analytical Program - Rocks Table 3-2. Rock Compositional Data Table 3-3. n-paraffin and Isoprenoid Distribution Table 3-4 Saturate Biomarker Ratios Table 3-5. Aromatic Biomarker Ratios Table 3-6. Individual Component Stable Carbon Isotope Data Table 3-7. Analytical Data Compilation for Interpretation Table 3-8. Total Organic Carbon and Rock-Eval Pyrolysis Table 3-9. Lithology of Rocks in Bitumen Extract Study Table Vitrinite Reflectance and Visual Kerogen Assessment

5 TABLE OF CONTENTS, continued Page No. List of Figures Figure 2-1. Figure 2-2. Figure 2-3. Figure 2-4. Figure 2-5. Figure 2-6. Figure 2-7. Figure 2-8. Figure 2-9. Pristane/nC17 versus Phytane/nC18 C15+ Stable Carbon Isotope Composition Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Carbon Isotope (del 13C) versus Carbon Number: Oils and Rocks Figure Pristane/Phytane versus Hopanes/Steranes Ratio Figure Pristane/Phytane versus C27/C29 Steranes Ratio Figure C19/C23 Tricyclics versus C24 Tetra/C26 Tri Figure C27, C28, C29 Sterane Compositions (abb, mz 218) Figure del Deuterium versus Pristane/Phytane Ratio Figure del Deuterium versus C27/C29 Steranes Ratio Figure Age Diagnostic Ternary Plot Figure 3-1. C15+ Stable Carbon Isotope Composition WELL RECORDS DISKETTES WITH OIL AND SOURCE ROCK DATA VOLUME 2 Analytical Data Volume on Oils Analyzed in this Study VOLUMES 3, 4, 5 Analytical Data Volume on Source Rocks Analyzed in this Study

6 EXECUTIVE SUMMARY The present study, completed for Idemits u Oil and Gas Company, Ltd., provides a detailed geochemical characterization of 42 crude oils and 11 condensates, and 73 extracts from source rocks of different ages (Tertiary, Cretaceous, Jurassic, Permian, Carboniferous, Devonian, and Ordovician) from the different Sub-Andean basins of Peru. The geochemical data on the hydrocarbon fluids and the source rocks were interpreted in order to classify the oils and condensates into genetic oil families, describe the geographic and stratigraphic distributions of the different oil families, identify the source rocks that generated the different oil families, and identify the petroleum systems present in the different Sub-Andean basins. Among the hydrocarbon fluids evaluated, 25 oils come from the Maranon Basin, 14 oils and 11 condensates from the Ucayali Basin, and three oils from the Madre de Dios Basin. Seventy-three source rocks of different ages/formations, evaluated by extract characterization, come from the Santiago, Bagua, Huallaga, Maranon, Ucayali, Ene, and Madre de Dios Basins. Seven genetic oil families, designated as A, B, C, D, D-1, E, and E-1, were recognized among the oils and condensates evaluated from the different Sub-Andean basins. Oils from Families A and B are in Cretaceous reservoirs and are located in the Maranon Basin. The oils from Families A and B were generated from the Cretaceous source rocks (shales, mainly Chonta). Oils from Family C are mainly in Cretaceous reservoirs (rarely in basal Tertiary) and are located in the Maranon and northern Ucayali Basins. The Family C oils were generated from the Jurassic Pucara source rocks (shales and calcareous shales). Oils and condensates from Families D, D-1, and E-1 are in

7 Cretaceous and Paleozoic reservoirs and are located in the Ucayali Basin. The oils and condensates from D and D-1 were derived from the Upper Paleozoic source rocks (shales, probably mainly Ene). The condensates from E-1 were derived from the Devonian source rocks (shales). The oils from Family E are from Paleozoic reservoirs in the Madre de Dios Basin and were also derived from the Devonian source rocks (shales). The source rocks for the oils from all families were marine and contained Type II kerogen with either predominantly marine algal-bacterial organic matter (as for A, B, C, D-1, and E) or mixed organic facies with significant terrigenous organic matter (as for D). The condensates from D, D-1, and E-1 were probably derived from low yield Type II or Type II/III kerogens. The oils and condensates from all families are mature. Knowledge of the distribution of the different oil families and of their source rocks, based on oil-source rock correlations, establishes the petroleum systems present in the Sub- Andean Basins. The Maranon Basin has two known petroleum systems related to the Cretaceous source rock (mainly Chonta) and the Jurassic source rock (Pucara). The Ucayali Basin has multiple known petroleum systems related to the Jurassic Pucara, the Upper Paleozoic (mainly Ene), and the Devonian source rocks. The Madre de Dios Basin has a known petroleum system related to the Devonian source rock.

8 Chapter 1 INTRODUCTION The present study, completed for Idemitsu Oil & Gas Company, undertakes a detailed geochemical evaluation of 41 crude oils and 11 condensates, and 73 source rocks ranging in age from Devonian to Cretaceous from the Sub-Andean Basins of Peru. Classification of crude oils and condensates in to genetic oil families, and oil-source rock correlations are essential to define the petroleum system or systems present in the Sub-Andean Basins. Perupetro has authorized Idemitsu to use and integrate the information from a number of previous studies including the non-proprietary 1996 Core Lab Sub-Andean Basin study, the 1995 DGSI report for Anadarko, and the 1998 Core Lab report for Pan Energy. The study integrates the results of new analyses on oils, condensates, and rocks with the existing information. Objectives The main objectives of this study are the following: 1. Classify the oils and condensates into genetic oil families. 2. Outline the geographic and stratigraphic extents of the different oil families. 3. Characterize the extracts from source rocks of different formations and ages. 4. Identify the source rocks for the different genetic oil families. Analytical Program Oils, condensates, and source rocks from the different Sub-Andean basins of Peru were analyzed in this study. Forty-one oils and 11 condensates from Maranon, Ucayali, and

9 Madre de Dios Basins were evaluated in this study, based on new analyses and data compiled from previous reports. Analyses carried out in this study on the hydrocarbon fluids include API gravity, sulfur content, whole oil GC, and saturate and aromatic carbon isotope ratios on three oils and nine condensates; LC separation, saturate and aromatic GC-MS on 28 oils and nine condensates; deuterium isotope ratios on whole oil from 35 oils and eight condensates; GC-IRMS carbon isotope ratios on n-alkanes and pristane and phytane from the saturate fractions of eight oils and four condensates. The analytical program for the oils and the condensates is given in Table 1-1. Seventy-three source rock samples were analyzed in this study for source rock characterization by extraction and extract characterization. Sixty-nine of these samples were previously analyzed in the Core Lab 1996 study for TOC, Rock-Eval pyrolysis, and visual kerogen analyses (kerogen type and vitrinite reflectance). Screening for source rocks was only done on 39 cuttings from three wells in this study (Rashaya Sur X, Chio X, and San Alejandro X) by TOC analysis (39 samples), pyrolysis (nine samples), and vitrinite reflectance measurements (21 samples), from which only four samples were selected for extraction. Based on extract quantity from the 73 samples, LC separation and whole extract deuterium isotope ratio were completed on 56 extracts, saturate and aromatic carbon isotope ratios on 57 extracts, whole extract GC on 73 extracts, saturate and aromatic GC-MS on 57 extracts, and GC- IRMS carbon isotope ratios on n-alkanes and pristane and phytane from the saturate fractions of 10 extracts. In addition, kerogen was isolated from 65 cutting samples, and carbon isotope ratio on kerogen was determined from 57 samples. The analytical program for the source rocks is given in Table 1-2. Outline Presentation of Results The analytical results and interpretation of this study are presented in five volumes. Volume 1 includes the interpretation of the analytical data. The organization of Volume 1 is given in the Table of Contents. Volume 2 contains the oil analytical data. Volumes 3, 4, and 5 contain the source rock analytical data. Analytical data and tables on the

10 oils and source rocks are also provided in diskettes. The organization of volume 1 is given in the Table of Contents. Volume 2 contains the oil analytical data. Volumes 3, 4, and 5 contain the source rock analytical data. Analytical data and tables on the oils and source rocks are also provided in diskettes.

11 Chapter 2 CHARACTERIZATION OF OILS AND CONDENSATES INTRODUCTION In this chapter, 41 oils and 11 condensates from the different Sub-Andean basins of Peru, are classified into genetic oil families. The samples include 25 oils from the Maranon Basin, 13 oils and 11 condensates from the Ucayali Basin, and three oils from the Madres de Dios Basin. The oils from the Maranon Basin were produced or tested from Cretaceous reservoirs; the oils and condensates from the Ucayali Basin come from both Cretaceous and Paleozoic reservoirs; and the oils from the Madres de Dios Basin are from Paleozoic reservoirs. Geochemical data evaluated on the 41 oils and 11 condensates include, when available, API gravity, sulfur content, gross compositional data from liquid chromatography (LC), whole oil gas chromatographic data (GC), gas chromatographymass spectrometry data (GC-MS) on saturates and aromatics, carbon isotope compositions on saturates and aromatics, deuterium isotope composition on whole oil, and gas chromatography-isotope ratio mass spectrometry data (GC-IRMS) on the saturate fraction. The sources of data on these oils and condensates are: this study, the 1996 Core Lab Speculative Study on the Sub-Andean basins of Peru, the DGSI report 95/3194 completed for Anadarko Petroleum Corporation, and the Core Lab Report for Pan Energy. Perupetro has authorized Idemitsu Oil and Gas Company to use available data from the previous reports for interpretation. Analyses carried out on the oils and condensates in this study are listed in Table 2-1. They include API gravity on five samples, liquid chromatography (SARA composition) on 31 samples, whole oil GC on nine samples, GC-MS on saturates and aromatics from 27 samples, carbon isotope compositions on saturates and aromatics from nine samples, whole oil deuterium isotope composition on 49 samples, and GC-IRMS on saturates from 12 samples. API, SARA composition, saturate and aromatic carbon

12 isotope compositions, and whole oil deuterium isotope composition are given in Table 2-2. Whole oil GC data, GC-MS data on saturates and on aromatics, and GCIRMS data on saturates are given in Tables 2-3, 2-4, 2-5, and 2-6, respectively. Table 2-1 provides a compilation of available data on the 41 oils and 11 condensates from different sources including this study that are used for interpretation. The samples are identified by well name, formation name, age and depth of reservoir, and basin name. Seven genetic oil families (A, B, C, D, D-1, E, and E-1) are recognized among the 41 oils and 11 condensates (Table 2-1). Different families of the oils were all derived from source rocks with Type II kerogens, but with certain variations of organic facies and depositional conditions. Condensates were probably derived from source rocks with low yield Type II or Type II/III kerogens. GENETIC OIL FAMILY A Among the 41 oils and 11 condensates evaluated in this study, two oils are grouped into Family A. They are from Dorissa-4 (DST #2, depth ft., Cretaceous Chonta reservoir) and Forestal 1A-51-1 (depth m, Cretaceous Vivian reservoir) in the Maranon Basin. The Dorissa-4 DST#2 oil was analyzed in this study for gross composition, δd on whole oil, saturate, and aromatic GC-MS. The Forestal 1A-51-1 oil was analyzed in this study only for δd on whole oil. All other data on the oils were compiled from previous reports. Organic Facies They are light oils with API of 34.7 and 33.5, respectively. The two oils are genetically related being derived from a common source rock (organic facies) with a Type II kerogen containing predominantly marine (algal-bacterial) organic matter and minor terrigenous/higher plant organic matter. The two oils have similar GC, saturate aromatic biomarkers, and saturate and aromatic carbon isotope characteristics. The predominantly marine organic matter source for the oils is indicated by pristane/phytane

13 ratios of , pristane/nc 17 ( ) versus phytane/nc 18 ( ) relationships (Figure 2-1), and saturate biomarker data, including tric yclic terpane distributions with the predominance of C 23 tricyclic terpane relative to C 19 tricyclic terpane (C 19 /C 23 tricyclic terpane ratios ), very high C 23 tricyclic/c 24 tetracyclic terpane ratios ( ), moderate hopanes/steranes ratios ( ), and C 27 /C 29 sterane ratios greater than 1.0 ( ). C 35 /C 34 homohopane ratios ( ) and the pristane/nc17 versus phytane/nc18 plots suggest moderately anoxic depositional conditions for the source rock of the oils. Gammacerane and oleanane are present in trace proportions relative to C 30 hopane. C 24 tetracyclic/c 26 tricyclics terpane ratios are low (0.20 in both oils). Diahopanes Y and Z are present. The C 28 /C 29 sterane ratios are Aromatic biomarker data available from the Dorissa-4 DST#2 oil show the presence of triaromatic dinosteranes in m/z 245 and m/z 231. A low dibenzothiophene/ phenanthrene ratio (DBT/PHEN) of 0.20, together with the pristane/phytane ratio of 1.3 suggest a marine shale source rock. The δ 13 C ratios of saturates and aromatics from the two oils are similar and isotopically heavy (saturate and 25.9; aromatic and 24.2), and plot in the field of marine oils (Figure 2-2). The whole oil δd ratios of the oils are also similar (-118and -121). Thermal Maturity The αββ/(αββ + ααα) C 29 sterane ratio of the Dorissa-4 DST# 2 oil is 0.68, which is close to an equilibrium value known to reach at the peak oil generation stage (about %Ro). In comparison, the 20S/(20S + 20R) C 29 ααα sterane ratio of 0.38 for the oil is low compared to its equilibrium value of about Such a low value is often observed in oils that reached the peak oil generation stage maturity. The 20S/(20S + 20R) C29 ααα sterane ratio of the Forestal 1A-51-1 oil is 0.56, which is an equilibrium value that is reached at the peak oil generation stage maturity. Ro estimates for the

14 Dorissa-4 DST#2 oil, based on MPI-1 and MPI-3, are 0.77 and 0.92 percent, respectively. GENETIC OIL FAMILY B Among the 41 oils and 11 condensates evaluated in this study, 10 oils are grouped into Family B. They are from Dorissa 4 (DST# ft., Vivian), Bartra-3 (DST#1, depth ft., Chonta), Bartra 1B-17-3 (depth m, Chonta), Huayuri Sur 1A-48-2 (depth m, Vivian), Huayuri Sur 1A-48-2 (depth m, Chonta), Capahuari Sur 1A-43-4 ( m, Chonta), San Jacinto 2 (DST#10, ft., Vivian), San Jacinto 2 (DST#4, depth m, Chonta), San Jacinto 2 (DST#6 depth ft., Chonta), and Tambo 1 (depth 3625m, Vivian). They are all from the Maranon Basin. In this study, all the 10 oils were analyzed for δd on whole oil. Gross compositional analysis and saturate and aromatic GC -MS were completed on the oils from Dorissa 4 DST#3, Bartra 3, Huayuri Sur 1A-48-2 ( m), San Jacinto 2 DST#6, and San Jacinto 2 DST#10. Gross compositional analysis and GC-IRMS on the saturate fraction were done on the oil from Tambo 1. API gravity and sulfur content were also determined from the Dorissa 4 DST#3 oil. All other data on the 10 oils were compiled from previous reports. Organic Facies The 10 oils show an API gravity range between 14.0 and The API gravity variation is caused by biodegradation. The two San Jacinto 2 DST#10 and Bartra 3 oils showing the lowest API of 14.0 and 17.4 are apparently the most severely degraded. The 10 oils are genetically related and were derived from a common source rock (organic facies) with a Type II kerogen consisting of predominantly marine (algalbacterial) organic matter and minor terrigenous/higher plant organic matter. The oils

15 are similar in GC, saturate and aromatic biomarkers, and saturate and aromatic carbon isotope characteristics. The predominantly marine organic matter source for the oils is indicated by pristane/phytane ratios of , pristane/nc 17 ( ) versus phytane/nc 18 ( ) relationships in the unaltered or lightly biodegraded oils (Figure 2-1), and saturate biomarker characteristics such as tricyclic terpane distributions with the predominance of C 23 tricyclic terpane relative to C 19 tricyclic terpane (C 19 /C 23 tricyclic terpane ratios ), very high C 23 tricyclic/c 24 tetracyclic terpane ratios ( ), low to moderate hopanes/steranes ratios ( ), and C 27 /C 29 sterane ratios greater than 1.0 ( ). The C 35 /C 34 homohopane ratios ( ) and the pristane/nc 17 versus phytane plots suggest moderate to highly anoxic depositional conditions for the source rocks for the oils. Gammacerane and oleanane are present in trace proportion relative to C30 hopane. The C24 tetracyclic/c26 tricyclics terpane ratios are low ( ). Diahopanes Y and Z are present. The C 28 /C 29 sterane ratios are of Aromatic biomarker data available from the Dorissa 4 DST#3, Bartra 3, Huayuri Sur 1A ( m), San Jacinto 2 DST#6, San Jacinto 2 DST#10, and Tambo 1 oils show the presence of triaromatic dinosteranes in m/z 245 and m/z 231. The low DBT/PHEN ratios of , together with the pristane/phytane ratios of suggest marine shale source rocks. The carbon isotope data available from the five Dorissa 4 DST#3, Bartra 3, Huayuri Sur 1A-48-2 ( m), San Jacinto 2 DST#10, and Tambo 1 oils show δ 13 C saturates between 26.2 and 28.9 and δ 13 C aromatics between 25.8 and The differences in aromatics δ 13 C values for the oils are within 1.0 ppt. The saturate δ 13 C values show a wider variation because of biodegradation. The most severely biodegraded oils, San Jacinto 2 DST#6 and Bartra 3, show relatively heavier δ 13 C saturates (-26.6 and 26.2) compared to the δ 13 C saturates (-27.8 to 28.9) of the other unaltered or lightly biodegraded oils. The oils, therefore, show good correlation among

16 them based on unaltered carbon isotope compositions. The oils plot in the field of marine oils in the diagram of δ 13 C saturates versus δ 13 C aromatics (Figure 2-2). The whole oil δd ratios of the oils are between 113 and 131. Figure 2-3 shows the GC- IRMS carbon isotope distribution of the C 15 + n-alkanes and the isoprenoids pristane and phytane from the saturate fraction from the Tambo 1 oil, a typical Family B oil. Thermal Maturity Thermal maturity of the Dorissa 4 DST#3, Bartra 3, Huayuri Sur 1A-48-2 ( m), San Jacinto 2 DST#6, San Jacinto 2 DST#10, and Tambo 1 oils are assessed based on the biomarker ratios 20S/(20S + 20R) C 29 ααα sterane, αββ/(αββ + ααα) C 29 sterane, MPI-1 and MPI-3. The αββ/(αββ + ααα) C 29 sterane ratios of are near equilibrium to equilibrium values and suggest the oils are mature being expelled from their source at or close to the peak oil generation stage (about %Ro). In comparison, the 20S/(20S + 20R) C 29 ααα sterane ratios of are significantly lower than the equilibrium values (around 0.55) and are often observed in oils that reached the peak oil generation maturity. Ro estimates, based on MPI-1 and MPI-3, are and percent, respectively. GENETIC OIL FAMILY C Among the 41 oils and 12 condensates evaluated in this study, 13 oils from the Maranon Basin and six oils from the Ucayali Basin represent the Oil Family C. The Maranon Basin oils are from the Corrientes XCD ( m, Chonta), Corrientes 115-D (2466m, Pozo Basal), Huaya 4X (DST# m, Vivian), Capirona X ( m, Chonta), Pavayacu XC ( m, Vivian), Pavayacu XC ( m, Chonta), Nueva Esperanza 86-D (DST#2, Chonta), Nueva Esperanza 74X (Vivian), Yanayacu 3 (Vivian), Yanayacu 38- X-C (DST#4), Valencia 25X (DST#5, Chonta), San Juan 77XD (DST#3, m, Chonta), and Chambira Este 124 (3625m) wells. The Ucayali Basin oils include five oils from the Maquia field, namely, Maquia 2 ( m, AA1), Maquia 5 (627.0-

17 630.5m, AA3-4), Maquia 12 (625m, Vivian), Maquia 16 ( m, AA1), and Maquia 16 ( m, AA2-4), and one oil from San Alejandro X. In this study, 16 of the oils were analyzed for δd on whole oil. Gross compositional analysis and saturate and aromatic GC-MS were completed on nine oils. GC-IRMS on the saturate fraction were done on three oils. All other data available on the 19 Family C oils were compiled from previous reports. Organic Facies Available API gravity of the Family C oils range between 22.0 and API gravity variation and low API are essentially due to biodegradation. The Family C oils show very similar GC, saturate and aromatic biomarkers, and saturate and aromatic carbon isotope characteristics. The oils were derived from a common source rock formation with a Type II kerogen containing essentially marine (bacterial-algal) organic matter deposited under moderate to highly anoxic conditions. Minor variation in organic facies and source rock lithology may exist. The marine organic matter contribution and anoxic depositional conditions are indicated by low pristane/phytane ratios (mostly , two oils greater than 1.0) and pristane/nc17 mostly less than phytane/nc18 with the exception of two oils (Figure 2-1). Among the saturate biomarkers, the tricyclic terpane distributions with the predominance of C 23 tricyclic terpane relative to C 19 tricyclic terpane (C 19 /C 23 tricyclic terpane ratios ), moderate hopanes/steranes ratios ( ), high C 23 tricyclic/c 24 tetracyclic terpane ratios ( ), C 27 /C 29 sterane ratios mostly close to 1.0 or greater ( ), suggest predominant contribution of marine algal-bacterial organic matter. Besides C 27 steranes, C 29 steranes may also have been partially derived from special algal type. The C35/C34 homohopane ratios vary between 0.66 and 1.13 suggesting moderate to highly anoxic depositional conditions. The C 24 tetracyclic/c 26 tricyclic terpane ratios are relatively high ( ). Gammacerane is

18 present in trace proportion relative to C 30 hopane. Diahopanes Y and Z are present in trace proportion or are absent. The C 28 /C 29 steranes are mostly between 0.68 and 0.84 (only two oils have higher values, 0.90 and 1.01). Oleanane is absent in the oils. Aromatic biomarker data from the oils show the presence of triaromatic dinosteranes in m/z 245 and m/z 231. The DBT/PHEN ratios show considerable variation ( ). The observed DBT/PHEN data with the pristane/phytane ratios mostly less than 1.0 and a few greater than 1.0 suggest marine depositional conditions and variable lithology of the oils source rocks (shale to lime mudstone). Carbon isotope data from the oils show δ 13 C saturates between 28.1 and 29.8, and δ 13 C aromatics between 26.3 and The oils plot in the field of marine oils in the diagram of δ 13 C saturates versus δ 13 C aromatics (Figure 2-2). The whole oil δd ratios of the oils range between 91 and 110 (mostly isotopically heavier than 100, i.e. mostly less negative numbers than 100). Figure 2-4 compares the GC-IRMS carbon isotope distributions of the C 15 + n-alkanes, and the pristane and phytane from the saturate fractions of the two Family C oils from Chambira Este 124 and Maquia 12. Minor differences exist between the two oils, probably reflecting the minor differences in organic source/depositional conditions as well as thermal maturity. Thermal Maturity The Family C oils are mature. The 20S/(20S + 20R) C29 ααα sterane ratios ( ) and αββ/(αββ + ααα) C 29 sterane ratios ( ) are lower than their corresponding equilibrium values (0.55 and 0.70, respectively). Anomalous and low values of these ratios are often observed in oils that passed the peak oil generation stage maturity ( %Ro). Ro estimated for MPI-1 and MPI-3 are %Ro and %Ro, respectively. The Maquia oils show greater than 1.0 %Ro maturity; and they are relatively more mature than the other Family C oils. GENETIC OIL FAMILY D

19 Three oils from the Ucayali Basin are grouped together in the Oil Family D. The oils are from La Colpa 1X (DST#7, ft., Cretaceous Agua Caliente), La Colpa 1X (1961.7m, Paleozoic Copacabana), and Sepa X (DST#4, m, Paleozoic Tarma). Besides, the condensate from Aguaytia 1 ( m, Agua Caliente) in the Ucayali Basin is also tentatively grouped under Family D. Analyses carried out in this study are δd on whole oil from La Colpa 1X DST#7 and δd on whole oil, LC separation (gross composition), and GC-IRMS on the saturate fraction from La Colpa 1X m. The Aguaytia 1 condensate was analyzed for LC separation (gross composition) and GC -IRMS on the saturate fraction. The rest of the data on the two La Colpa 1X oils and the Aguaytia condensate, and all data on the Sepa X DST#4 oil were compiled from previous reports. Organic Facies Two La Colpa oils are of relatively low API gravity ( ). API gravity of the Sepa oil is not available. However, based on its higher saturates content and higher saturates/aromatics ratio, the Sepa oil should have a relatively higher API gravity than that of the La Colpa oils. The two La Colpa oils are biodegraded. The La Colpa oils and the Sepa oil are genetically related to a common source rock, based on similarities in GC, saturate and aromatic biomarkers, and saturate and aromatic carbon isotope characteristics. The oils were derived from a low yield Type II source rock containing a mixed organic facies with mainly marine organic matter (algal and relatively minor bacterial) and significant terrigenous/higher plant organic matter, deposited under suboxic conditions. Moderately high pristane/phytane ratios ( ) and the pristane/nc 17 versus phytane/nc 18 relationship (Figure 2-1) suggest the contribution from a mixed organic facies with mainly marine organic matter and significant higher plant material, and suboxic depositional conditions. Low hopanes/steranes ratios ( ) and low C 27 /C 29 sterane ratios ( ) suggest

20 contribution of high algal plus higher plant material (both in relatively high proportions) compared to low bacterial organic matter. Low C 19 /C 23 tricyclic terpane ratios ( ) and moderately high C 23 tricyclic/c 24 tetracyclic terpane ratios ( ) support the mixed organic facies with abundant algal organic matter and significant higher plant material. The C 24 tetracyclic/c 26 tricyclics terpane ratios are low ( ). Low C 35 /C 34 homohopane ratios ( ) suggest suboxic depositional conditions. Gammacerane is absent or present in trace proportion relative to C30 hopane. Diahopanes X, Y, and Z are present in significant proportion. The C 28 /C 29 sterane ratios are Aromatic biomarker data of the La Colpa oils and the Sepa oil show the absence of triaromatic dinosteranes in m/z 245 and m/z 231. Low DBT/PHEN ratios of , together with the pristane/phytane ratios of , suggest a marine shale source rock. The δ 13 C ratios of saturates and aromatics from the La Colpa oils and the Sepa oil are similar (saturates to -29.1, aromatics to -28.7) and plot in the field of marine oils (Figure 2-2). The whole oil δd values available from the La Colpa oils are -122 and Figure 2-5 shows the GC-IRMS carbon isotope distribution of the C 15 + n-alkanes, and the pristane and phytane from the saturate fraction of the oil from La Colpa 1X m. The Aguaytia 1 condensate (API 54.6 ) is tentatively grouped under Oil Family D, based on its similarity with the La Colpa oils and the Sepa oil by its high pristane/phytane ratio (1.82), the pristane/nc 17 versus phytane/nc 18 relationship (Figure 2-1), moderately high C 19 /C 23 tricyclic terpane ratio (0.97), moderate C 23 tricyclic/c 24 tetracyclic terpane ratio (2.48), the presence of diahopanes X, Y, and Z, which also suggest a mixed organic facies and suboxic depositional conditions. However, compared to the source of the La Colpa oils and the Sepa oil, the source rock of the Aguaytia condensate contained much more bacterial organic matter and much less algal plus higher plant material (algal organic matter may be in higher or near equal proportion compared to higher

21 plant organic matter) as shown by the high hopanes/steranes ratio of 10.05, the C 27 /C 29 sterane ratio of 1.06, and the C 19 /C 23 tricyclic terpane ratio of The C 24 tetracyclic/c 26 tricyclics terpane ratio is Biomarker concentrations are low; therefore, the calculated biomarker ratios are very approximate. Aromatic biomarkers show absence of triaromatic steranes in m/z 245 and m/z 231. The δ 13 C of saturates and aromatics is and -25.4, and it plots in the field of marine (Figure 2-2). However, compared to the La Colpa oils and the Sepa oil, the saturates and aromatics isotopic values of the Aguaytia condensate are heavier, which probably reflects its relatively higher maturity compared to the oils (difference in organic facies might also have influenced the isotope values). GC-IRMS carbon isotope distribution of the C 15 + n-alkanes, and the pristane and phytane from the saturate fraction of the Aguaytia condensate are shown in Figure 2-6. Thermal Maturity The two La Colpa oils and the Sepa oil of the Family D oils are mature. Based on Core Laboratories 1996 study, the 20S/(20S + 20R) C 29 ααα sterane and αββ/(ααα + αββ) C 29 sterane ratios in the oils are low and anomalous as the maturity of the oils are apparently past the peak oil generation stage maturity ( %Ro). Ro maturity equivalent estimated from MPI-1 is percent. The Aguaytia condensate is also mature. Its maturity was assessed between 0.95 and 1.0 %Ro in the Core Lab 1996 study from the C 7 ratio, 2,4DMP/2,3DMP. GENETIC OIL FAMILY D-1 Four oils from the Agua Caliente field in the Ucayali Basin are grouped in the Oil Family D-1. These oils were produced from the Agua Caliente 10 ( m), Agua Caliente 33 ( m), Agua Caliente 6 ( m), and Agua Caliente 7 (893, Cretaceous Cushabatay) wells. Besides, the condensate from San Martin 1X

22 (Cushabatay/Agua Caliente) in the Ucayali Basin is also tentatively grouped under the Oil Family D-1. Analyses carried out in this study are API gravity, sulfur content, δd on whole oil, LC separation, whole oil GC, saturate and aromatic GC-MS, saturate and aromatic carbon isotope ratios on the oils from Agua Caliente 10 and Agua Caliente 33; δd on whole oil, LC separation, and saturate and aromatic GC-MS on the oils from Agua Caliente 6 and Agua Caliente 7; δd on whole oil; and GC -IRMS on the saturate fraction on the San Martin 1X condensate. The rest of the data on the samples were compiled from previous studies. Organic Facies The four Agua Caliente oils are light oils with API between 34.0 and The four oils are very similar in GC, saturate and aromatic biomarkers, saturate and aromatic carbon isotopes, and whole oil deuterium isotope characteristics, indicating a common source rock for the oils. The oils were derived from a Type II source rock with a mixed organic facies containing mainly marine (algal-bacterial) organic matter and minor terrigenous/higher plant organic matter, deposited under suboxic conditions. Moderately high pristane/phytane ratios ( ) and the pristane/nc 17 versus phytane/nc 18 relationship (Figure 2-1) suggest the mixed organic facies with mainly marine organic matter and suboxic depositional conditions. Moderate hopanes/sterane ratios ( ), C 27 /C 29 sterane ratio slightly greater than 1.0 ( ), low C 19 /C 23 tricyclic terpane ratios ( ), and moderate C 23 tricyclic/c 24 tetracyclic terpane ratios ( ) suggest the contribution of mixed organic facies with mainly marine algal-bacterial organic matter and relatively minor higher plant material. The C 24 tetracyclic/c 26 tricyclics terpane ratios are moderately high ( ). The C 35 /C 34 homohopane ratios are low ( ) suggesting suboxic depositional conditions. Gammacerane is present in trace proportion relative to C30 hopane. The diahopanes X, Y, and Z are present in significant proportion. The C 28 /C 29 sterane ratios are

23 Aromatic biomarker data of the four Agua Caliente oils show absence of triaromatic dinosteranes in m/z 245 and m/z 231. Low DBT/PHEN ratios of , together with the pristane/phytane ratios of suggest a marine shale source rock. The δ 13 C ratios of saturates and aromatics from the four Agua Caliente oils are very similar (saturates to 28.5, aromatics to 27.8) and plot in the field of marine oils (Figure 2-2). The whole oil δd values are also similar (-113 to -116, average values). Comparison of GC-IRMS carbon isotope distributions of the C 15 + n-alkanes, and the pristane and phytane from the saturate fractions of the two oils from Agua Caliente 7 and Agua Caliente 33, also shows their close similarity (Figure 2-7). The San Martin condensate (API 44.5 ) is grouped in this study under Oil Family D-1. This condensate was previously grouped with Oil Family D in the Core Lab 1996 study. We consider the present grouping is more reliable. The San Martin condensate is very similar to the D-1 Agua Caliente oils in carbon isotope compositions (San Martin condensate saturates 28.2, aromatics 27.4; Agua Caliente oils saturates 28.4 to 28.5, aromatics 27.5 to 27.8), and whole oil δd values (San Martin condensate - 116, Agua Caliente oils to 116). Besides, GC-IRMS carbon isotope distribution of the nc 7 -nc 27 and the pristane and phytane of the San Martin condensate is similar to that of the oils from Agua Caliente 33 and Agua Caliente 7 (compare Figures 2-6 and 2-7). GC and biomarker data do not support unequivocally one way or the other. Biomarker concentrations are low; therefore, the calculated biomarker ratios are very approximate. The San Martin condensate has a pristane/phytane ratio of 1.12 whereas the pristane/phytane ratios of both Family D and Family D-1 oils are greater than 1.5. Hopanes/steranes ratio of the condensate (0.98) is closer to that of Family D oils ( ) than Family D-1 oils ( ). The C 23 tricyclic/c 24 tetracyclic terpane ratio of the condensate (5.38) is closer to that of Family D oils ( ) than Family D-1 oils ( ). The C 24 tetracyclic/c 26 tricyclic terpane ratio of the condensate (0.61) is closer to that of Family D-1 oils ( ) than Family D oils ( ). The C19/C23

24 tricyclic terpane ratio of the condensate is 0.59, while this ratio, in both Family D and D- 1 oils, is in the range of The C27/C29 sterane ratio is high (1.83). Thermal Maturity The Agua Caliente oils of Family D-1 are mature. The αββ/(ααα + αββ) C 29 sterane ratios and 20S/(20S + 20R) C29 ααα sterane ratios of the oils are and Some of these values are probably altered (somewhat lowered) as the oils apparently reached the equilibrium stages of these sterane ratios. Ro estimated for the oils from MPI-1 is between 0.77 and 0.86 percent. Ro for the oils based on MPI-3 is between 0.91 and 0.93 percent. GENETIC OIL FAMILY E Three oils from the Pariamanu N ( m, Carboniferous), Pariamanu 1 (3780m, Carboniferous Ambo), and Puerto Primo 2X (DST#3, m, Devonian Cabanillas) wells in the Madre de Dios Basin are included in the Oil Family E. Analyses carried out in this study are δd on whole oil from all samples and GC-IRMS on the saturate fraction on Pariamanu 1, 3780m. The rest of the data were compiled from previous studies. Organic Facies The three oils are light oils with API between 40 and 47. The oils are similar in GC characteristics. The moderate to high pristane/phytane ratios ( ) and the pristane/nc 17 versus phytane/nc 18 relationship (Figure 2-1) suggest a mixed organic facies with very significant higher plant material (probably a low yield Type II), and suboxic depositional conditions. The pristane/nc 17 versus phytane/nc 18 relationships also suggest the oils are very mature.

25 Biomarkers are absent in the Puerto Primo oil due to high maturity. The Pariamanu oils show only minor biomarkers due to high maturity. The Pariamanu oils have moderate hopanes/steranes ratios of and very high C 19 tricyclic/c 23 tetracyclic terpane ratio (3.61, data available on Pariamanu 1). The Pariamanu N oil also shows other terpanes and steranes in minor proportion having a high C 24 tetracyclic/c 26 tricyclics terpane ratio of 0.72, a C 27 /C 29 sterane ratio of 1.02, and a C 28 /C 29 sterane ratio of It also shows the presence of diahopanes and a high Ts/Tm ratio. The overall biomarker characteristics suggest a mixed organic facies with mainly marine (algal-bacterial) organic matter and abundant higher plant material. Among aromatic biomarkers that are in very low proportions, triaromatic dinosteranes are not detected in m/z 245 and m/z 231. The δ 13 C ratios of saturates and aromatics from the three oils are similar (saturates to -29.2, aromatics to ), and plot in the field of marine to transitional marine-non marine oils (Figure 2-2). The three oils also similar δd ratios (-120 to -127). Figure 2-8 shows the GC-IRMS carbon isotope distribution of nc 14 -nc 34, and the pristane and phytane from the saturate fraction of the Pariamanu 1 oil. Thermal Maturity Thermal maturity of the Pariamanu oils and the Puerto Primo oil cannot be estimated for lack of biomarkers and biomarker maturity ratios. The very low pristane/nc17 and phytane/nc 18 ratios ( and , respectively) and the very low biomarker concentrations, however, suggest high thermal maturity. GENETIC OIL FAMILY E-1 Nine condensates from the Cashiriari field in the Ucayali Basin are grouped in the Oil Family E-1. The condensates were produced from Cashiriari 3 (DST#1, m, Permian Nol/Ene), Cashiriari 3 (DST#2B m, Permian Nia), Cashiriari 3 (DST#3, m, Chonta), Cashiriari 3 (DST#4A, m, Vivian), Cashiriari

26 3X (2533m, Permian Shinal), Cashiriari 3X ( m, Nia), Cashiriari 3X (2577m), Cashiriari 1( X) (DST#1, m, Noi/Ene), and Cashiriari 1( X) (DST# m, Nia). Analyses carried out on the first six condensates are API gravity, sulfur content, δd on whole oil, LC separation, whole oil GC, saturate and aromatic GC-MS, and saturate and aromatic carbon isotope ratios. One of these six condensates, the Cashiriari 3 DST#2B, was also analyzed by GC-IRMS on saturates. Analyses carried out on the next two condensates are whole oil δd, LC separation, and saturate and aromatic GC- MS. Analyses completed on the last condensate are δd on whole oil and GC-IRMS on saturates. The rest of the data on the condensates were compiled from previous studies. Organic Facies Cashiriari condensates range in API between 51.4 and The condensates were apparently derived from a common source rock based on similarities in GC, saturate and aromatic biomarkers, saturate and aromatic carbon isotopes, δd on whole oil, and GC-IRMS carbon isotope distribution of the nc 12 -nc 27, and the pristane and phytane from the saturate fraction. High pristane/phytane ratios ( ) and the pristane/nc 17 versus phytane/nc 18 relationship (Figure 2-1) suggest a Type II/III source rock with mixed organic facies and suboxic depositional conditions. Biomarker concentrations in the condensates are very low. Therefore, the ratio calculations are very approximate. Hopanes/steranes ratios vary between 1.15 and The majority of the condensates (six samples) show C 27 /C 29 sterane ratios greater than 1.0 (four samples , two samples ). Only one sample shows a low C 27 /C 29 sterane ratio of The C 19 /C 23 tricyclic terpane ratios are quite variable and high ( ). The C 23 tricyclic/c 24 tetracyclic terpane ratios are low to high varying between 1.21 and The C24 tetracyclic/c26 tricyclic terpane ratios are high varying between These biomarker

27 characteristics suggest a mixed organic facies with varying proportions of algal, bacterial and higher plant material, but always with significant to abundant higher plant material. The diahopanes X, Y, and Z are present. The C 34 and C 35 homohopanes are absent or in extremely low concentrations due to suboxic depositional conditions and high maturity. The C 28 /C 29 sterane ratios are between 0.51 and Aromatic biomarker data from the Cashiriari condensates show the absence of triaromatic dinosteranes in m/z 245 and m/z 231 with one exception. The sample from Cashiriari 3X m shows the presence of triaromatic dinosteranes in m/z 245 which is not expected. Low DBT/PHEN ratios of , together with the high pristane/phytane ratios ( ), suggest mainly marine shales. The δ 13 C ratios of saturates and aromatics are very similar among the condensates (saturates to -26.2, aromatics to ). The whole oil δd ratios are also very similar (-110 to -119). Comparison of GC-IRMS carbon isotope distributions of the nc 13 -nc 28 and the pristane and phytane from the saturate fractions of the two Cashiriari condensates (Cashiriari 3X 2577m and Cashiriari 3 DST#2B) also show their close similarity (Figure 2-9). Thermal Maturity The Cashiriari condensates are very mature. Thermal maturity of a Cashiriari condensate was estimated to be about 1.00 %Ro, based on the C 7 maturity ratio. Low biomarker concentrations also suggest their high maturity. Ro ranges bas ed on MPI-1 and MPI-3 are and percent, respectively. MPI-3 values are probably more reliable and also agree with the C 7 maturity. COMPARISON AMONG THE GENETIC OIL FAMILIES Classification of oils into genetic oil families identifies the oil families generated from different source rocks or different source rock organic facies. Geochemical

28 characteristics used for genetic classification are, therefore, related to source rock organic facies/depositional conditions and geologic age. Based on these geochemical characteristics, seven genetic oil families (A, B, C, D, D-1, E, and E-1) have been described from the Sub-Andean basins of Peru in the previous chapter. In the following discussion, a comparative analysis of these characteristics is provided, which helps separate the different genetic oil families from each other. The source rocks of all the families are marine sediments which probably contained Type II kerogens (high to low yield) with varying amounts of algal, bacterial, and terrigenous/higher plant organic matter and varying depositional conditions. The geochemical parameters or ratios used for genetic oil grouping are pristane/phytane, pristane/nc 17, phytane/nc 18, hopanes/ steranes, C 27 /C 29 sterane, C 19 /C 23 tricyclic terpane, C 24 tetracyclic/c 26 tricyclics terpane, C 28 /C 29 sterane, presence or absence of dinosteranes, presence or absence of oleanane, δd on whole oil, and GC-IRMS carbon isotope distribution of the n-alkanes and the pristane and phytane from the saturate fraction. A number of cross plots or triangular plots using these ratios have been constructed to define the distinguishing characteristics of the different oil families. Figure 2-1 is the pristane/nc 17 versus phytane/nc 19 relationships for all the genetic oil families based on available data. The diagram quite nicely separates several of the oil families based on organic source differences and maturity. Biodegradation, if present, separates the oils from the same family, but the trend remains unaltered. Families A and B plot in a closely related cluster and cannot be separated from each other in this diagram, as both have the same predominantly marine organic facies. Family C oils, derived from more marine organic source deposited under more reducing conditions can be separated from the oils from Family A/Family B, even though overlapping relationship may exist. Family D oils and condensate derived from a mixed organic facies, plot along a long trend because of biodegradation and maturity effects (two of the three oils are biodegraded, the condensate is more mature than the oils). The Family D-1 oils, also derived from a mixed organic facies, cannot be separated from Family D oils. Compared to Family D and Family D-1 oils, Family E oils and Family E-1 condensates were derived from mixed organic facies with relatively more

29 terrigenous/higher plant contribution. Family E-1 condensates show partially overlapping relationship with Family D oils. The field of Family E oils includes the Family D condensate. Figure 2-10 shows the cross plots of pristane/phytane ratio versus hopanes/steranes ratio for the different oil families. In this diagram, separations of the families D, D-1, C, and E1 from each other are clearly exhibited. Family A and Family B cannot be separated from each other, and the field of A/B partially overlaps the field of C. Family E and Family E-1 cannot be separated from each other. Figure 2-11 is a cross plot of pristane/phytane ratio versus C 27 /C 29 sterane ratio for the different oil families. The diagram separates A/B, typical C, D, D-1, and E/E-1, but again cannot discriminate between A and B or between E and E-1. Figure 2-12 is a cross plot of C 19 /C 23 tricyclic terpane ratio versus C 24 tetracyclic/c 26 tricyclics terpane ratio. In this diagram, Families A and B cluster together and C and D- 1 cluster together, while separations of A/B, D, C/D-1, E, and E-1 are evident. Figure 2-13 shows the plots of the different oil families in the C 27 -C 28 -C 29 sterane diagram. The C 27 -C 28 -C 29 sterane compositional plots show overlapping relationships among the different oil families. The diagram is not very useful to separate the different oil families of the Sub-Andean basins of Peru. The δd ratios on whole oil of Family C oils are very distinct (lowest negative values, -91 to -110) than that of the other oil families. Families A, B, D, and E show the highest negative values (-113 to 131). Even though partly overlapping with Families A, B, and E, the Families D-1, and E-1 show intermediate values (-110 to 116). Therefore, the δd versus pristane/phytane diagram (Figure 2-14) and the δd versus C 27 /C 29 sterane diagram (Figure 2-15) are useful to separate several of these oil families. In the δd versus pristane/phytane diagram, Family C and Family E-1 clearly separate from each other and from the rest of the oil Families A, B, D, D-1, and E. Families A, B, D, D-1,

30 and E show overlapping relationship and they cannot be separated from each other in this diagram. In the δd versus C 27 /C 29 sterane diagram, Family C is clearly separated from A/B, D, and the rest of the oil families, while A/B, D-1, E-1, and E show overlapping relationship among them. The δ 13 C saturates versus δ 13 C aromatics diagram (Figure 2-2) is the only diagram that can discriminate between Family A and Family B. These two families have essentially the same geochemical characteristics (GC and biomarker characteristics, δd ratios) other than saturate and aromatic carbon isotope compositions. It suggests these two oil families were probably derived from the same organic facies differing only slightly in depositional conditions. The presence or absence of dinosteranes, which has age connotation (see Chapter 4 on oil-source rock correlation) is very useful to separate the oils from Families A, B, and C from the oils from Families D, D-1, E, and E-1. Based on the general knowledge of dinosterane occurrences in marine sediments through geologic time (Moldowan et al., 1995, Peters and Moldowan, 1993), data on source rocks from the 1996 Core Lab study, and this study, absence of dinosteranes can be indicative of Paleozoic age, while the presence of dinosteranes may imply Mesozoic and younger ages. The presence or absence of oleanane also has age connotation. Oleanane, derived from angiosperm flowering plants, is present in Middle/Late Cretaceous to younger sediments and is absent in Jurassic or older sediments (Peters and Moldowan, 1993). Oleanane in trace proportion is ubiquitous in Cretaceous marine sediments and abounds in Tertiary sediments. Presence of dinosteranes, together with absence of oleanane or presence of oleanane in trace proportion, separate Family C and Families A/B, respectively. Absence of dinosteranes and absence of oleanane are typical of Families D, D-1, E, and E-1. It implies the Family C oils were derived from Triassic/Jurassic age source rocks, the oils of Families A and B were derived from Cretaceous age source rocks, and the oils/condensates from D, D-1, E, and E-1 were derived from Paleozoic source rocks. The C28/C29 sterane ratio also appears to have age connotation. The C28/C29 ratio of marine source rocks appears to increase in a systematic way from older to younger