New Methodology for Estimating Unconventional Production and Long Term Performance

Transcription

1 New Methodology for Estiating Unconventional Production and Long Ter Perforance Ian Walton, Ph.. Senior Research Scientist Reserves Estiation Unconventionals Houston August 6 Project I 4

2 Unconventional Production Production fro ulti-fractured long horizontal wells Ultra-low ereability reservoir Most gas resident in the ores Presence of a colex network of natural fractures

3 Outline Quantifying well roductivity Short-ter Mediu-ter Long-ter Single-hase: gas, oil Multi-hase: gas/oil Relating roductivity to key araeters Reservoir roerties Coletions araeters Oerational araeters Estiating long-ter recovery fro liited roduction data

4 water roduction (bbl/day) gas rodcution (Mscf/day) roduction rate (bscf/year) Soe Shale Gas Production ata tie (years),6,4,, tie (days) water rate drawdown gas rate Baihly et al (SPE 35555)

5 daily roduction Conventional Production ata Analysis Techniques: ecline Curve Analysis daily roduction, Mscf/day cuulative roduction, bscf 5 data "b=.6" "b=" 5 data "b=.6" "b=" "b=.6" "b=" tie (days) tie (days) Conventional ecline Analysis Ars qi q for b b ( b t) i Advantages Quick, easy to use, failiar isadvantages Liited basis in the hysics Not aroriate for transient flow No insights into roduction drivers Exonent b is assued to be constant

6 Shale Gas Production Models Nuerical, incororating flow in atrix and fracture networks discrete fracture network continuu odel (dual orosity/dual ereability) Sei-analytic, continuu odel (dual orosity/dual ereability) erturbation solution aroriate for shale gas reservoirs

7 Quantifying Productivity: Production Coefficient Theory suggests that for a substantial eriod of tie cuulative roduction and roduction rate can be aroxiated by Q where C C t, q deends on Pressures (bhf, ore or reservoir ressure) Reservoir quality/ GIP (ereability, orosity) Gas roerties (viscosity, coressibility, equation of state) Productive fracture surface area C t C A r s w c k T c L k

8 roduction rate (bsc/yearf) cuulative roduction (scf) New Production ata Analysis Method OL NEW tie (years) sqrt(tie) years^.5 Plot cuulative roduction against the square-root of tie: exect straight line Sloe of the line is the best etric of well roductivity: Production Coefficient Solution is valid for any years of roduction Production data analysis is efficient and effective: data fro thousands of wells have been analyzed Provides a rational basis for evaluating the roduction drivers, quantifying what akes a good well, assessing lay-by-lay variations and evaluating the role of natural fractures.

9 cuulative roduction Iact of Coletions Paraeters ft sacing 5 ft sacing y = 7.9x y =.976x sqrt (tie) 5 Ratio of roduction coefficients =.4 C A r s w c k Ratio of # fractures = 35/5 =.4 Iact on EUR?

10 Iact of Variable rawdown Granite Wash ata (SPE 638)

11 cuulative roduction Early-tie Transient Regie Barnett Fayettville Woodford Haynesville sqrt (tie) (sqrt(onths))

12 water roduction (bbl/day) gas rodcution (Mscf/day) Identification of Flow Regies,6,4,, tie (days) water rate drawdown gas rate Transient regie I Transient regie II Boundaryiacted regie

13 q dt dq ecline rate and Ars exonent dt d dt d b Ars exonent: 4 ) ( b T e Q q e Q Q t t Boundary-iacted regie Linear Flow regie b t t C q k L c T

14 Variation of Ars b-exonent Transient regie I Transient regie II Boundaryiacted regie Terinal decline rate: % b=?? b= b=

15

16 Cuulative Oil (bbl) New Estiates of Terinal ecline Rate and EUR Terinal decline rate 4 T T c L k Fro roduction data, identify oint at which linear flow ends: t t elf Q Q Fro the sei-analytic solution transition to boundary doinated regie (exonential decline) begins (linear flow ends) at about elf telf. 5T elf sqrt (tie) (Months After Initial Production)^.5

17 Cuulative Oil (bbl) New Estiates of Terinal ecline Rate and EUR 4 T T c L k telf. 5T New estiate of terinal decline rate. elf telf T New estiate of EUR sqrt (tie) (Months After Initial Production)^.5

18 Cuulative Oil (bbl) Iact of Terinal ecline Rate on EUR Q elf C t elf C t elf T Q Q elf 4 t elf 4 T T c L k Q C sqrt (tie) (Months After Initial Production)^.5

19 ecline Rates: Suary Shale gas wells roduce in the infinite acting regie for any years. For instantaneous drawdown, decline rate ~ /t, indeendent of the value of the roduction coefficient. Variable drawdown in the first few onths of roduction ay reduce the early-tie decline rate, and it is often negative. Terinal decline rate is not arbitrary: it is related to the tie at the end of linear flow. Ars b-exonent varies in tie in a rational anner.

20 Soe key results Better characterized shale gas roduction through several stages of roduction including early-tie transient, linear flow and boundary-doinated flow. Methodology of resenting and analyzing roduction data using an alternative etric for shale gas roductivity the Production Coefficient. Identified the ajor roduction drivers in ters of reservoir and coletion araeters. Iroved estiates of future roduction in coarison to conventional techniques. eonstrated technique for estiating recovery fro a liited aount of roduction data.

21 Thank You! Ian Walton, Ph.. Senior Research Scientist Reserves Estiation Unconventionals Houston August 6 Project I 4