Seismic Reservoir Prediction in Lengjia-Leijia Area

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1 Applied Mechanics and Materials Online: ISSN: , Vol. 318, pp doi: / Trans Tech Publications, Switzerland Seismic Reservoir Prediction in Lengjia-Leijia Area Qi Zhou 1, a, Wenlong Ding 2,b 1 Northeast Petroleum University at Qinhuangdao,Qinhuangdao,China 2 School of Energy Resources, China University of Geosciences, Beijing, China a qizh_dq@yahoo.com.cn, b dingwenlong2006@126.com Keywords: seismic reservoir prediction; oil-gas reservoir; deep exploration; logging-constrained inversion; Lengjia-Leijia area Abstract. Through the deep exploration in Lengjia-Leijia area, four reservoirs were found: the lower sub-section of the third member of Shahejie formation, the fourth member of Shahejie formation, Mesozoic, and Archean. The fourth member of Shahejie formation and the layer below it had fewer drilling reach; its reservoir stratums are different. Seismic reservoir prediction has become the major means of oil-gas reservoir evaluation. The logging-constrained inversion method was applied in this study. A geologic model was established based on the detailed interpretation of seismic data; then, inversion and prediction were performed to describe and evaluate the distribution, thickness, and physical characteristics of the reservoirs. The results showed that the reservoir in the fourth member of Shahejie formation, Mesozoic, and Archean are well developed, and that oil-gas accumulation is in good condition. Therefore, the deep layer in this area is an important exploration direction. This study also provided the preliminary prediction that a favorable trap area exists. Introduction The oil-gas exploration in Lengjia-Leijia area began in the 1970s. The first member of the Shahejie formation oil-gas reservoir and the third member of the Shahejie formation oil-gas reservoir were successively discovered in the Lengjia area. In the Leijia area, the third member of the Shahejie formation oil-gas reservoir was found in The fourth member of the Shahejie formation oil-gas reservoir was found in At present, the exploration of the fourth member of the Shahejie formation, Mesozoic, and Archean is at a very low degree; only about 10 exploratory wells were drilled in the fourth member of the Shahejie formation. Preliminary studies suggest that the four layers have suitable oil-gas accumulation conditions, and their exploration potential is tremendous. Their exploration is therefore an important step [1-3]. Stratum Overview The Lengjia-Leijia area is located in the middle of the western sag of the Liaohe Basin. It is adjacent to the Taian Fault and the Central Uplift in the east. Its eastern part is a slope-break zone, and its western part belongs to the Chenjia sub-sag. The stratum exposed by drilling shows that Archean metamorphic rocks constitute the base of the area; the cap rocks are mainly Mesozoic and Cenozoic. The Liaohe Basin is the Mesozoic-Cenozoic back-arc continental rift, and the rift sequence is composed of five Paleogene structural sequences. Each structural sequence is in unconformable contact with the others [4-5]. Four reservoirs were developed the deep below the third member of the Shahejie formation in the Lengjia-Leijia area.the third member of the Shahejie formation belongs to the steep-sloped fan-delta deep lake slump turbidite sedimentary system, and the fan-delta facies sandy conglomerate is thick. Primary interparticle pore and micropore are its major pore types, and its major pore structures are characterized by medium porosity, low to extremely low permeability, and -micro-fine throat. The fourth member of the Shahejie formation belongs to gentle-sloped fan-delta shallow lake carbonate rock sedimentary system. Fracture is its main pore type, and its main pore structures are characterized by low porosity step, low to extremely low permeability, and -micro-fine throat. Mesozoic belongs to All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-08/04/16,23:54:46)

2 Applied Mechanics and Materials Vol the alluvial fan and volcanic rock sedimentary system. Sandy conglomerate and volcanic breccias are its primary lithologic structures. Fracture and solution pore are its main pore types, and low porosity, low to extremely low permeability, and -micro-fine throat characterize its main pore structures. Archean belongs to the metamorphic rock sedimentary system and mainly consists of migmatite. It also includes gneiss, mylonite, lamprophyre, diabase, amphibolites, and medium-acidity veins. Fracture, microfracture, interparticle pore, and solution pore are its main pore types. Method of seismic reservoir prediction Seismic reservoir prediction has become the major means of oil-gas reservoir evaluation in low exploration areas and has contributed to the oil-gas exploration and development process [6-21]. The current study applied the logging-constrained inversion method based on the model in the Strata inversion software to address the specific geological characteristics of the reservoirs' lithology. Fine calibration of synthetic seismogram. The corresponding relationship between the reservoir and the reflecting wave group of the seismic section was established through horizon calibration. This relationship is the key link in the process of inversion. The quality of the wavelet is an important factor in the accuracy of the horizon calibration. Prior to structural interpretation, we made use of the Syntool module in the Landmark software to produce a synthetic seismogram and to accurately calibrate the larger stratigraphic framework as well as to determine the boundaries of the second member of the Shahejie formation, the third member of the Shahejie formation, and the fourth member of the Shahejie formation. Seventeen wells were selected through the E-log module of the Strata inversion software to carry out 3 rounds of wavelet extraction and horizon calibration for the fine calibration of the small layers. Establishing the geologic model. A three-dimensional structural model was established through seismic-geologic horizon calibration and fine interpretation of seismic data and through the analysis of the structural section and fault system. The initial geologic model or wave impedance model, which was interpolated and extrapolated according to the order of the sedimentary bodies in the structural model framework, was established based on the logging information and drilling data. Inversion test of the backbone section. The size of the wave impedance inversion exhibited not only a distinct hierarchy but also a close correlation with the lithologic changes and sandbody distribution. Through the inversion test of backbone section, this paper confirms that the seismic data from the Lengjia-Leijia area have a relatively high signal-to-noise ratio (SNR) and the effect of the inversion method on the model is positive. The inversion test determined each inversion parameter, including impedance variation range, iteration, and scale factor. Among these parameters, the impedance variation range caused the final results of the inversion to be almost similar to the initial model. This constraint reduced the multiple solutions of the inversion results, which led to over-dependence on the initial model. Therefore, the initial model must be as similar to the actual subsurface model as possible. Credibility of the inversion results. The specific inversion parameters suitable for the exploration target were determined and three-dimensional wave impedance inversion was performed after the establishment of the initial geologic model and the inversion test of the backbone section. Quality control must be established during inversion. A synthesized seismic section was extracted every 10 CDP following the inline of the inversion body and in the direction of the crossline. The result of the comparison of the inversion section, residual section, and original seismic section reveals that the similarity between the synthesized seismic section and the original seismic section was controlled. Thus, inversion residue was minimized and the validity of the inversion results was ensured. Conclusion and comprehension of the reservoir prediction Reservoir horizon. Seismic inversion clearly showed that the reservoirs are mainly distributed in the lower sub-section of the third member of the Shahejie formation and the stratum below. The reservoir stratum above the middle sub-section of the third member of the Shahejie formation is undeveloped, and the reservoir body gradually broadens from top to bottom. Longitudinally, the wave impedance

3 International Conference on Machinery, Materials Science and Energy Engineering body of the target layer in the Lengjia-Leijia area is divided into four hierarchical wave impedance layers. From top to bottom, these are: the wave impedance layer of the upper sub-section of the third member of the Shahejie formation with low impedance as background; the wave impedance layer of the middle sub-section of the third member of the Shahejie formation with poor sandstone continuity; the wave impedance layer of the lower sub-section of the third member of the Shahejie formation with interbedded sandstone and good sandstone continuity; and the wave impedance layer of the fourth member of the Shahejie formation and Mesozoic. Although the sub-sag exhibited less constraint, several continuously developed reservoirs with high impedance were still observed. Horizontal distribution of reservoirs. The above plane graph of the wave impedance shows that the source was mainly injected from the east side to the sub-sag. During the sedimentation of the fourth member of the Shahejie formation, the source was abundant and could cross from the center of the sub-sag to the sediment section in the west. During the sedimentation of the middle and lower sub-section of the third member of the Shahejie formation, the source was relatively abundant and could also cross from the center of the sub-sag to the sediment section in the west; however, the distance was short. During the sedimentation of the upper sub-section of the third member of the Shahejie formation, only an insignificant amount of sandbody was found in the sub-sag. Lithologic character of the reservoir stratum. Through the calibration of the known well and the application of the wave impedance prediction, three types of structures were found in the reservoir stratum. These were sandy conglomerate between the lower sub-section of the third member of the Shahejie formation and the fourth member of the Shahejie formation, the breccias in Mesozoic, and the migmatite in Archean. These structures mostly belonged to the fissure reservoir with low permeability and low porosity. The effects of these structures were complicated; thus, prediction was difficult. Trap. Continuous tectonic movement and rapid sedimentation formed the various traps and oil-gas reservoirs in the Lengjia-Leijia area, including various anticlinal traps, fault traps, stratigraphic traps, and lithologic traps. Based on the inversion results of the seismic data, this paper calibrated and tracked the grit rock mass with oil in the Lei 77 well in the fourth member of the Shahejie formation and the grit rock mass with oil and gas in the Chengu 2 well in the Mesozoic. The paper also developed two lithologic traps. The buried hill trap in Archean was also evaluated. References [1] Qi Zhou, Wenglong Ding, Xulong Liu, Shuang Nie, Structural characteristics and trap research of Liaohe western depression Lengjia-leijia area, Petroleum Geology and Engineering,2011,25(3): [2] Qi Zhou, Xulong Liu, Shuang Nie, Jianjun Jiao, Deep oil and gas accumulation conditions in Lengjia-Leijia area of Liaohe basin, Lithologic Reservoirs,2011,23(4): [3] Juncheng Ju, Mesozoic reservoir formating conditions in the south of west sag of Liaohe deperession and its exploarion directions, Journal of Oil and Gas Technology,2007,29(3): [4] Yuqing Wang, Jingming Song, Weigong Meng, Cuixian Meng, Xiaojun Wu, Effect of integrated geological interpretation of Xinglongtai-Majuanzi buried-hill belt in Liaohe depression, China Petroleum Exploration,2007,12(4): [5] Hongbin Sun, Fenglian Zhang, Structural-sedimentary evolution characteristics of paleogene in Liaohe depression, Lithologic Reservoirs,2008,20(2): [6] Gang Chen, Zhihao Qu and Shengliang Zhao, Comprehensive restrictive inversion technique and its application to lateral reservoir prediction in Gaoyang 3-D exploration area, Oil Geophysical Prospecting, 2000,35(4):

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5 2013 International Conference on Machinery, Materials Science and Energy Engineering / Seismic Reservoir Prediction in Lengjia-Leijia Area /

Main controlling factors of hydrocarbon accumulation in Sujiatun oilfield of Lishu rift and its regularity in enrichment

35 3 2016 9 GLOBAL GEOLOGY Vol. 35 No. 3 Sept. 2016 1004 5589 2016 03 0785 05 130062 P618. 130. 2 A doi 10. 3969 /j. issn. 1004-5589. 2016. 03. 019 Main controlling factors of hydrocarbon accumulation