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Well Performance Analysis in a Multiwell Gas Condensate Reservoir— Arun Field, Indonesia

Well Performance Analysis in a Multiwell Gas Condensate Reservoir— Arun Field, Indonesia. Presented at SPE Advanced Technology Workshop Well Testing in Gas Condensate Reservoirs 1-2 April 2000, Calgary, Alberta, Canada. T. Marhaendrajana, Texas A&M University

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Well Performance Analysis in a Multiwell Gas Condensate Reservoir— Arun Field, Indonesia

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  1. Well Performance Analysis in a Multiwell Gas Condensate Reservoir— Arun Field, Indonesia Presented at SPE Advanced Technology Workshop Well Testing in Gas Condensate Reservoirs 1-2 April 2000, Calgary, Alberta, Canada T. Marhaendrajana, Texas A&M University N.J. Kaczorowski, Mobil E&P (U.S.) T.A. Blasingame, Texas A&M University

  2. Summary—Well Test Analysis • A representative summary of the analysis and interpretation of well test data taken from the Arun Gas Field (Sumatra, Indo-nesia) (Single-phase gas analysis is used). • 2-zone radial composite reservoir model is effective for diagnosing the effects of con-densate banking at Arun Field. • Application of a new solution for the analysis and interpretation of well test data that exhibit "well interference" effects.

  3. Summary—Production Data Analysis • Analysis and interpretation of production data using (single-phase) decline type curve analysis: • Permeability-thickness product • Skin factor • Original and movable gas-in-place • Comparison of results from well test and production data analyses vary—but these variations appear to be consistent.

  4. Field Description • Located in Northern part of Sumatra, Indonesia • Retrograde gas reservoir • One of the largest gas fields in the world • Arun Field has 111 wells: • 79 producers • 11 injectors • 4 observation wells • 17 wells have been abandoned N General Information—Arun Field (Indonesia) Arun Field

  5. Major Phenomena Observed at Arun Field • Liquid accumulation near wellbore (conden-sate banking) • Need to know the radial extent of the condensate bank for the purpose of well stimulation. • Well interference effects (well test analysis) • Well interference effects tend to obscure the "standard" flow regimes—in particular, the radial flow response. • This behavior influences our analysis and inter-pretation efforts, and we must develop an alter-native analysis approach for well test data affected by multiwell interference effects.

  6. Well Test Analysis Strategy • Condensate banking phenomenon: • Used a 2-zone radial composite reservoir model—the inner zone represents the "con-densate bank," and the outer zone represents the "dry gas reservoir." (reported kh-values are for the "outer zone") • Well interference effects: • Developed a new method for the analysis of well test data from a well in multiwell reservoir where we treat the "well interference" effect as a "Regional Pressure Decline." (This pheno-mena is observed in approximately 35 cases)

  7. Well Test Analysis: Examples • Well C-I-18 (A-096)—Test Date: 28 Sep. 1992 • Radial composite effects. • Multiwell interference effects. • Well C-IV-01 (A-060) [Test Date: 25 Feb. 1993] • Radial composite effects. • Multiwell interference effects.

  8. WT Example 1: Log-log Summary Plot Raw data Corrected Improvement of pressure derivative. Infinite-acting Reservoir Model (Does not include non-Darcy flow) Pseudopressure Functions, psi Condensate banking region. Higher mobility region. Closed boundary at 160 ft? (includes non-Darcy flow). Effective shut-in pseudotime, hrs

  9. WT Example 1: Horner (Semilog) Plot Well C-I-18 (A-096) [Test Date: 28 September 1992] Condensate banking region. Higher mobility region. Shut-in Pseudopressure, psia Raw data Corrected Horner pseudotime, hrs (tp = 1.56 hr)

  10. WT Example 1: Muskat Plot (single well pavg plot) Well C-I-18 (A-096) [Test Date: 28 September 1992] pp,avg = 1148.6 psia Data deviate from the "Muskat line" —indicating interference effects from surrounding wells. Onset of boundary dominated flow (single well analogy). Shut-in pseudopressure, psia "Transient flow" dppws/dDta, psi/hr

  11. WT Ex. 1: "Well Interference" Plot (radial flow only) Well C-I-18 (A-096) [Test Date: 28 September 1992] Intercept is used to calculate permeability. Slope is used in the pressure correction. (Dpp')Dtae, psi (Dpp')Dtae <0, indicating multiwell interference effects. Dta2/ Dtae

  12. WT Example 2: Log-log Summary Plot Well C-IV-01 (A-060) [Test Date: 25 February 1993] Raw data Corrected Improvement of pressure derivative. Pseudopressure Functions, psi Condensate banking region. Closed boundary at 330 ft? (includes non-Darcy flow). Infinite-acting Reservoir Model (Does not include non-Darcy flow) Higher mobility region. Effective shut-in pseudotime, hrs

  13. WT Example 2: Horner (Semilog) Plot Well C-IV-01 (A-060) [Test Date: 25 February 1993] Condensate banking region. Shut-in Pseudopressure, psia Higher mobility region. Raw data Corrected Horner pseudotime, hrs (tp = 2.61 hr)

  14. WT Example 2: Muskat Plot (single well pavg plot) Well C-IV-01 (A-060) [Test Date: 25 February 1993] pp,bar = 1573.5 psia Onset of boundary dominated flow. Shut-in pseudopressure, psia "Transient flow" dppws/dDta, psi/hr

  15. WT Ex. 2: "Well Interference" Plot (radial flow only) Well C-IV-01 (A-060) [Test Date: 25 February 1993] Intercept is used to calculate permeability. (Dpp')Dtae <0, indicating multiwell interference effects. (Dpp')Dtae, psi Slope is used in the pressure correction. Dta2/ Dtae

  16. Correlation of Well Test Results—Arun Field • Maps: • kh (outer-zone (gas) permeability). • skin factor. • non-Darcy flow coefficient. • Radius of condensate bank. • Correlation of non-Darcy flow coefficient and the permeability-thickness product (kh).

  17. kh Map • kh distribution ap-pears reasonable. • 3 major "bubbles" of kh noted, pro-bably erroneous. • kh shown is for the "outer" zone (when the radial compo-site model is used).

  18. Skin Factor Map • Skin factor distri-bution appears very consistent. • Areas of "high skin" indicate need for individual well stimulations. • Skin factors are calculated based on the "inner" zone of the radial compo-site model (when rc-model is used).

  19. D (Non-Darcy) Map • This map indicates a uniform distribution. • "high" and "low" regions appear to be focused near a single well. • Relatively small data set (30 points).

  20. Condensate Radius Map • Good distribution of values—"high" spots probably indicate need for individual well stimulations. • Relatively small data set (32 points).

  21. D (Non-Darcy)—kh Crossplot • D-kh crossplot indi-cates an "order of magnitude" correla-tion. • Verifies that non-Darcy flow effects are systematic. Slope = 2

  22. Production Data Analysis: Arun Field • Well C-I-18 (A-096) • Limited history (no EURMB analysis possible). • Erratic performance. • Reasonable match on decline type curve. • Well C-IV-01 (A-060) • Good history (well was down for almost two years in 1993-1995). • Sparse p/z data for EURMB analysis. • Early data match on decline type curve is questionable. • Late performance data deviate from material balance trend on decline type curve, indicat-ing "well interference" effects.

  23. WPA Example 1: Well History Plot

  24. WPA Example 1: Decline Type Curve Plot Fetkovich-McCray Decline Type Curve (No Well Interference Effects)

  25. WPA Example 2: Well History Plot

  26. WPA Example 2: EURMB Plot

  27. WPA Example 2: Decline Type Curve Plot Fetkovich-McCray Decline Type Curve (No Well Interference Effects)

  28. WPA Example 2: Decline Type Curve Plot Fetkovich-McCray Decline Type Curve (Includes Well Interference Effects)

  29. Correlation of Production Analysis Results—Arun Field Production data analyzed using decline type curve analysis—single-phase (gas) pp and ta used. Flow Properties: Volumetric Properties: • Maps: • kh • skin factor • Crossplots: • khWT—khWPA • sWT—sWPA • Plots: • G vs. time • EURMB vs. time • kh vs. time • Crossplots: • G—EURMB • EURPI—EURMB

  30. kh Map • kh shown is com-puted using decline type curve analysis on early production (pp and ta used). • kh distribution ap-pears reasonable (albeit lower than WT estimates). • A few "bubbles" of kh noted, these are probably erroneous.

  31. Skin Factor Map • Skin factors com-puted using decline type curve analysis on early production. • Skin factors from WPA are lower than WT estimates.

  32. khWT—khWPA Crossplot • khWT estimates are clearly higher than khWPA estimates. • khWT estimates are "current," khWPA estimates are "ini-tial." • Variation is system-atic—decline type curve analysis uses earliest production data for kh (and s) estimates.

  33. sWT—sWPA Crossplot • sWT estimates are "current," sWPA estimates are "ini-tial." • Could argue that this plot shows the "evolu-tion" of the skin fac-tor. • sWPA estimates should be higher, tied to kh estimation in decline type curve analysis.

  34. Gas Reserves from Decline Type Curve Analysis

  35. Estimated Ultimate Recovery from Material Balance

  36. Flow Capacity (kh) from Decline Type Curve Analysis

  37. G (Decline Type Curve)—EURMB Crossplot • G-EURMB crossplot indicates excellent agreement of com-puted results.

  38. EURPI—EURMB Crossplot • EURPI—EURMB cross-plot shows excellent correlation of results. • Verifies that these analyses are consis-tent.

  39. Well Performance Analysis in a Multiwell Gas Condensate Reservoir— Arun Field, Indonesia Presented at SPE Advanced Technology Workshop Well Testing in Gas Condensate Reservoirs 30 September- 1 October 1999, Houston, TX. T. Marhaendrajana, Texas A&M University N.J. Kaczorowski, Mobil E&P (U.S.) T.A. Blasingame, Texas A&M University

  40. Well Test Analysis: Examples (extra) • Well C-IV-11 (A-084)—Test Date: 5 Jan. 1992 • Multiwell interference effects. • Well C-IV-11 (A-084)—Test Date: 4 May 1992 • Radial composite effects. • Multiwell interference effects.

  41. Example 3: Log-log Summary Plot Well C-IV-11 (A-084) [Test Date: 5 January 1992] Raw data Corrected Improvement on pressure derivative. Pseudopressure Functions, psi Closed boundary at 150 ft? (includes non-Darcy flow). Infinite-acting Reservoir Model (Does not include non-Darcy flow) Effective shut-in pseudotime, hrs

  42. Example 3: Horner (Semilog) Plot Well C-IV-11 (A-084) [Test Date: 5 January 1992] Shut-in Pseudopressure, psia Raw data Corrected Horner pseudotime, hrs (tp = 1.62 hr)

  43. Example 3: Muskat Plot (single well pavg plot) Well C-IV-11 (A-084) [Test Date: 5 January 1992] pp,bar = 1920 psia Onset of boundary dominated flow. Shut-in pseudopressure, psia "Transient flow" dppws/dDta, psi/hr

  44. Example 3: "Well Interference" Plot (radial flow only) Well C-IV-11 (A-084) [Test Date: 5 January 1992] Intercept is used to calculate permeability. Slope is used in the pressure correction. (Dpp')Dtae, psi Presence of multiwell interference effects is unclear Dta2/ Dtae

  45. Example 4: Log-log Summary Plot Well C-IV-11 (A-084) [Test Date: 4 May 1992] Raw data Corrected Improvement on pressure derivative. Pseudopressure Functions, psi Condensate banking region. Infinite-acting Reservoir Model (Does not include non-Darcy flow) Closed boundary at 197 ft? (includes non-Darcy flow). Higher mobility region. Effective shut-in pseudotime, hrs

  46. Example 4: Horner (Semilog) Plot Well C-IV-11 (A-084) [Test Date: 4 May 1992] Condensate banking region. Shut-in Pseudopressure, psia Higher mobility region. Raw data Corrected Horner pseudotime, hrs (tp = 1.63 hr)

  47. Example 4: Muskat Plot (single well pavg plot) Well C-IV-11 (A-084) [Test Date: 4 May 1992] pp,bar = 1882.8 psia Onset of boundary dominated flow. Shut-in pseudopressure, psia "Transient flow" dppws/dDta, psi/hr

  48. Example 4: "Well Interference" Plot (radial flow only) Well C-IV-11 (A-084) [Test Date: 4 May 1992] Intercept is used to calculate permeability. Slope is used in the pressure correction. (Dpp')Dtae, psi (Dpp')Dtae >0, no clear indication of multiwell interference effects. Dta2/ Dtae

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