ExxonMobil Texas A

1
ExxonMobil Texas AM PTA/PA Project Cerro Negro
Field (Venezuela)
Discussion Meeting (25 April 2007)
Sara Coulthard, Texas AM U. Dilhan Ilk, Texas
AM U. Thomas A. Blasingame, Texas AM
U. Department of Petroleum Engineering Texas AM
University College Station, TX 77843-3116
2
Objectives

• To estimate reservoir/volumetric properties for
  specified well drain-age areas within the
  Cerro-Negro Field using production rate and
  pressure histories (i.e., Production Analysis
  (PA)) and Pressure Transient Analysis (PTA)).
• Reservoir Parameters
• (PA/PTA) Effective permeability to oil (ko), md
• (PA/PTA) Near-well skin factor (shor or srad),
  dimensionless
• (PA/PTA) Anisotropy factor (kv/kh), dimensionless
  (kv/kh lt 1)
• (PTA) Wellbore storage coefficient (Cs), RB/psi
• (PTA) Effective horizontal well length (Lw), ft
• (PTA) Time-dependent skin factor (sf(t)),
  dimensionless (not preferred)
• Volumetric Parameters
• (PA) Contacted oil-in-place (N), STB (est. using
  constant ct value)
• (PA) Drainage area (per well basis) (A), acre
• (PA/PTA) Initial reservoir pressure (per well
  basis) (pi), psia
• (PA) Average reservoir pressure (per well basis)
  (pavg), psia
• Production/Pressure Match/Forecast
• qo(t) and pwf(t) model-based match
• qo(t) or pwf(t) model-based forecast
• To provide a qualitative assessment of the
  distribution of reservoir properties (mapping
  results)

3
Deliverables

• Well Summaries (.ppt and .pdf files delivered
  for well)
• PA and PTA parameters.
• Various analysis/forecasts plots and specific
  analysis plots.
• Discussion orientation, discussion of results,
  etc. (on slides).
• Final Report (MS Word and .pdf files)
• Discussions, conclusions, recommendations of this
  work.
• Appendices all results
• Tables,
• Plots, and
• Maps, etc.
• Data inventory all files ( provided in a
  library)
• .xls,
• .ktz/.ks3 (Kappa), and
• .fkt/.rta (Fekete), etc.

4
PA/PTA Methodology Analysis/Interpretation
Process

• Analysis/Interpretation Process
• PLOT historical data
• Semilog rate and Cartesian pressure data ("strip
  chart" plot). (base plot)
• Log-log (pi-pwf)/qo vs. Np/qo diagnostic
  plot. (model identification plot)
• Cartesian pwf vs. qo "IPR" plot. (checks
  "correlation of pwf and qo data)
• ESTIMATE recovery (EUR)
• Semilog rate vs. time. (Arps exponential/hyperboli
  c relations)
• Cartesian qo vs. Np EUR plot. (Simple recovery
  estimation plot)
• PERFORM model-based analysis of production (PA)
  data.
• Log-log (pi-pwf)/qo vs. Np/qo ("Log-log"
  plot). (Base diagnostic plot)
• Log-log qo/(pi-pwf)/qo vs. Np/qo ("Blasingame"
  plot). (Secondary diagnostic plot)
• Log-log qo and Np vs. t ("Fetkovich"
  plot). (Log-log "history" plot)
• Other specialized plots (flowing material
  balance, etc.). ("Confirmation" plots)
• Initialize reservoir model, then history match to
  refine parameters.
• PERFORM model-based analysis of well test (PTA)
  data.
• Log-log (pws-pwf,Dt0) or derivative vs. t
  ("Log-log" PTA plot). (Base PTA plot)
• Semilog pws vs. log(Dt) ("Semilog" plot). (Base
  PTA plot)
• Semilog pws vs. log(tpDt/)Dt ("Horner"
  plot). (Base PTA plot)
• Same process as PA, initialize reservoir model,
  then history match PTA data.

5
Inventory

• Data (Transferred)
• PAD 2 CH203, 204, 206, 208, 209, 212, 213, 214,
  219
• PAD 3 CG302, 312, 314, 315
• PAD 4 CG401, 402, 403, 404, 405, 413, 415
• PAD 5 CH502, 505, 507, 508, 509, 511, 513, 515,
  516
• PAD 6 CH601, 602, 603, 604, 605, 606, 607, 608,
  612, 613, 614, 615, 616, 617, 618
• PAD 7 CH701, 702, 703, 704, 705, 706, 707, 708,
  709, 710, 711, 712, 713, 714

6
Issues

• Pad 2
• CH 203 PTA can not be performed (Abnormal
  pressures during national strike)
• CH 204 High quality data until April 2002
• CH 206 Ok
• CH 208 Bad data Dec 02 -- Mar 03 (PTA can not
  be performed)
• CH 209 Ok
• CH 212 Ok
• CH 213 Ok
• CH 214 Erratic data and data from multiple
  gauges (major problem)
• CH 219 Ok

• Pad 3
• CG 302 Ok
• CG 312 100 psia jump during national strike
  (PTA can not be performed)
• CG 314 Ok
• CG 315 Ok

7
Issues

• Pad 4
• CG 401 Ok
• CG 402 Ok
• CG 403 Ok
• CG 404 Ok
• CG 405 Only daily OFM data available (PTA can
  not be performed)
• CG 413 NO RATES/ Small amount of high quality
  pressure data (NO ANALYSIS)
• CG 415 Scatters in data, issues in the high
  quality data (PTA can not be performed)

• Pad 5
• CH 502 Ok
• CH 505 Ok
• CH 507 Ok
• CH 508 Ok
• CH 509 Ok
• CH 511 Ok
• CH 513 Ok
• CH 515 Ok
• CH 516 Ok

8
Issues

• Pad 6
• CH 601 Ok
• CH 602 Ok
• CH 603 OFM data are erratic
• CH 604 Ok
• CH 605 Ok
• CH 606 Ok
• CH 607 Ok
• CH 608 Ok
• CH 612 Ok
• CH 613 Ok
• CH 614 Ok
• CH 615 Ok
• CH 616 Ok
• CH 617 Ok
• CH 618 Missing sensor pressure data Jun 01
  Dec 02

Data resolution is relatively lower in pad 6.
9
Issues

• Pad 7
• CH 701 Ok
• CH 702 Ok
• CH 703 Ok
• CH 704 Ok
• CH 705 Ok
• CH 706 Ok (bad data Oct 02 Nov 02 pressures
  138000 psia??)
• CH 707 Ok (bad data Oct 02 Nov 02 pressures
  127000 psia??)
• CH 708 Ok (bad data Oct 02 Nov 02 pressures
  126000 psia??)
• CH 709 Ok (bad data Oct 02 Nov 02 pressures
  131000 psia??)
• CH 710 Ok
• CH 711 Ok (missing pressures for 5 days (21 Dec
  02 26 Dec 02)
• CH 712 Ok
• CH 713 Ok
• CH 714 Ok

10
PA Results from Topaze (KTZ) Sensor Data Well CH
203

• Discussion PA Results from Topaze (KTZ) Sensor
  data used
• Horizontal well model in a finite-acting
  reservoir.
• Reasonable match.
• Note that this is the very early part of analysis
  to identify issues.

11
PA Results from Topaze (KTZ) OFM Data Well CH 203

• Discussion PA Results from Topaze (KTZ) OFM
  data used
• Horizontal well model in a finite-acting
  reservoir.
• Reasonable match very close values with the
  analysis using sensor data.
• OFM data is reliable several gaps in the sensor
  data.

12
PTA Results from Saphir (KS3) Sensor Data Well
CH 203

• Discussion PTA Results from Saphir (KS3)
  Sensor data used
• Reasonable history match.
• Sensor data during national strike are very
  problematic (see next slides).
• Values from Topaze are used to initiate the
  analysis (close results).

13
PTA Results from Saphir (KS3) OFM Data Well CH
203

• Discussion PTA Results from Saphir (KS3) OFM
  data used
• Reasonable history match except for the later
  part.
• Noisy pressure derivative average pressures?.
• Values from Topaze are used to initiate the
  analysis (close results).

14
Data Issues (Sensor) Well CH 203

• Discussion Issues
• Data between 18 Dec 02 and 21 Dec 02 strange
  pressure behavior.
• Sensor data are missing after 21 Dec 02 (I used
  OFM data to fill the gap).
• Missing data between 21 Dec 02 and 18 Feb 03.

15
Data Issues (Sensor) Well CH 203

• Discussion Issues
• Data between 18 Dec 02 and 21 Dec 02 strange
  pressure behavior.
• Sensor data are missing after 21 Dec 02 (I used
  OFM data to fill the gap).
• Missing data between 21 Dec 02 and 18 Feb 03.

16
Data Issues (Sensor) Well CH 203

• Discussion Issues
• Abnormally high sensor pressures between 25 Oct
  03 and 03 Jan 04.
• They do not show up in the OFM data.

17
PA Results from Topaze (KTZ) OFM Data Well CH 203

• Discussion PA Results from Topaze (KTZ) OFM
  data used
• Horizontal well model in a finite-acting
  reservoir.
• Reasonable match very close values with the
  analysis using sensor data.
• OFM data is reliable several gaps in the sensor
  data.

18
PA Results from Topaze (KTZ) OFM Data Well CH 206

• Discussion PA Results from Topaze (KTZ) OFM
  data used
• Horizontal well model in a finite-acting
  reservoir.
• Good match needs to be improved.
• OFM data is reliable.

19
PA Results from Topaze (KTZ) OFM Data Well CH 208

• Discussion PA Results from Topaze (KTZ) OFM
  data used
• Horizontal well model in a finite-acting
  reservoir.
• Very good match.
• OFM data is reliable will yield closer values
  to real analysis using sensor.

20
PA Results from Topaze (KTZ) OFM Data Well CH 212

• Discussion PA Results from Topaze (KTZ) OFM
  data used
• Horizontal well model in a finite-acting
  reservoir.
• High GOR values are taken into account for the
  calculation of total rate.
• Above match is obtained with the well length (Lw)
  2500 ft.

21
PA Results from Topaze (KTZ) OFM Data Well CH 212

• Discussion PA Results from Topaze (KTZ) OFM
  data used
• Horizontal well model in a finite-acting
  reservoir.
• High GOR values are taken into account for the
  calculation of total rate.
• Above match is obtained with the rectangular
  boundaries (3x1).

22
ExxonMobil Texas AM PTA/PA Project Cerro Negro
Field (Venezuela)
Analysis Summary (PTA/PA) for Well CH 517
Dilhan Ilk, Texas AM U. Thomas A. Blasingame,
Texas AM U. Department of Petroleum
Engineering Texas AM University College
Station, TX 77843-3116 (Ilk) 1.979.458-1499
dilhan_at_tamu.edu (Blasingame) 1.979.845.2292
t-blasingame_at_tamu.edu
23
PA Results from Topaze (KTZ) FAHW Well CH 413

• Discussion PA Results from Topaze (KTZ)
  Rectangular Reservoir
• Horizontal well model in a FINITE-acting
  reservoir much better match.
• FAHW model performs well for model/analysis
  functions, except early times.
• Excellent rate and pressure history match,
  correlates well with PTA.

24
PTA Results from Saphir (KS3) FAHW Well CH 413

• Discussion PTA Results from Saphir (KS3)
  Rectangular Reservoir
• FAHW model yields EXCELLENT match all times.
• FAHW model yields OUTSTANDING match of PTA data.
• Minor deviation in pressure matches (PA and PTA)
  due to pi differences.

25
ExxonMobil Texas AM PTA/PA Project Cerro Negro
Field (Venezuela)
Analysis Summary (PTA/PA) for Well CH 517
Sara Coulthard, Texas AM U. Dilhan Ilk, Texas
AM U. Thomas A. Blasingame, Texas AM
U. Department of Petroleum Engineering Texas AM
University College Station, TX 77843-3116
26
Input Data Summary Well CH 517

• Comment Input Data Summary
• cf given by ExxonMobil staff.
• co, cw, cg computed from PVT data given by
  ExxonMobil staff.
• So, Sw, Sg given by ExxonMobil staff.

27
PA Results Summary Well CH 517

• Comment PA Results Summary
• Good agreement in permeability (kradial or kavg)
  all analyses.
• Kappa Engineering results forced (Saphir and
  Topaze) for consistency.
• RTA (Fekete) results comparable (not forced,
  wanted independent estimates).

28
PA Results from Topaze (KTZ) IAHW Well CH 517

• Discussion PA Results from Topaze (KTZ)
  Infinite-Acting Reservoir
• Excellent history match (Production history
  plot).
• Analysis plots SUGGEST finite-acting reservoir
  behavior.
• A clear definition of the reservoir drive must be
  made.

29
PA Results from Topaze (KTZ) FAHW Well CH 517

• Discussion PA Results from Topaze (KTZ)
  Rectangular Reservoir
• Excellent history match and match of analysis
  plot functions.
• This analysis STRONGLY SUGGESTS finite-acting
  reservoir behavior.
• Depletion drive is apparent.

30
PA Results from RTA (Fekete) FAHW Well CH 517

• Discussion PA Results from RTA (Fekete)
  Rectangular Reservoir
• RTA pressure match is excellent (similar results
  to Topaze).
• RTA does not presently compute rates from the
  analytical solution.
• Decline type curve is very convincing
  depletion-drive reservoir.

31
PTA Results Summary Well CH 517

• Comment PTA Results Summary
• Good agreement in permeability (kradial or kavg)
  all analyses.
• Fekete and Kappa Engineering results are
  consistent.
• pi lower for PTA due to computational approach
  (pi backcalculated from pwf).

32
PTA Results from Saphir (KS3) IAHW Well CH 517

• Discussion PTA Results from Saphir (KS3)
  Infinite-Acting Reservoir
• This analysis is a balance of "history match" and
  analysis plots.
• History match is excellent (infinite-acting
  reservoir).
• "Better" match of the PTA data obtained by the
  sacrifice of the history match.

33
PTA Results from Saphir (KS3) FAHW Well CH 517

• Discussion PTA Results from Saphir (KS3)
  Rectangular Reservoir
• Slightly better PTA data match using a finite
  (rectangular) reservoir model.
• Minor differences in results for PTA
  infinite/finite-acting reservoir cases.
• PTA/PA (Saphir/Topaze) results are forced.

34
PTA Results from Saphir (KS3 Best Fit) IAHW Well
CH 517

• Discussion PTA Results from Saphir (KS3)
  Infinite-Acting Reservoir
• "Best fit" of PTA data OUTSTANDING match of PTA
  functions, BUT ...
• Conclusion PTA can be manipulated to fit data,
  but without the "constraint" of the production
  history (and PA), the PTA may just be analysis of
  artifacts.

35
Input Data Summary Well CH 517 (h 120 ft)

• Comment Input Data Summary
• cf given by ExxonMobil staff.
• co, cw, cg computed from PVT data given by
  ExxonMobil staff.
• So, Sw, Sg given by ExxonMobil staff.

36
PA Results Summary Well CH 517 (h 120 ft)

• Comment PA Results Summary
• k 15600 md (h 77 ft) ? k 14900 md (h 120
  ft).
• sh 0.08 (h 77 ft) ? sh 0.07 (h 120 ft).
• OOIP 95.0 MMSTB (h 77 ft) ? OOIP 81.4 MMSTB
  (h 120 ft).

37
PA Results from Topaze (KTZ) FAHW Well CH 517 (h
120 ft)

• Discussion PA Results from Topaze (KTZ)
  Rectangular Reservoir
• Excellent history match and match of analysis
  plot functions.
• This analysis STRONGLY SUGGESTS finite-acting
  reservoir behavior.
• Depletion drive is apparent.

38
PTA Results Summary Well CH 517 (h 120 ft)

• Comment PTA Results Summary
• k 15600 md (h 77 ft) ? k 14900 md (h 120
  ft).
• sh 0.08 (h 77 ft) ? sh 0.07 (h 120 ft).
• OOIP 95.0 MMSTB (h 77 ft) ? OOIP 81.4 MMSTB
  (h 120 ft).

39
PTA Results from Saphir (KS3) FAHW Well CH 517
(h 120 ft)

• Discussion PTA Results from Saphir (KS3)
  Rectangular Reservoir
• Slightly better PTA data match using a finite
  (rectangular) reservoir model.
• Minor differences in results for PTA
  infinite/finite-acting reservoir cases.
• PTA/PA (Saphir/Topaze) results are forced.

40
ExxonMobil Texas AM PTA/PA Project Cerro Negro
Field (Venezuela)
Discussion Meeting (25 April 2007)
Sara Coulthard, Texas AM U. Dilhan Ilk, Texas
AM U. Thomas A. Blasingame, Texas AM
U. Department of Petroleum Engineering Texas AM
University College Station, TX 77843-3116