ALASKA OIL AND GAS CONSERVATION COMMISSION
3001 Porcupine Drive
Anchorage Alaska 99501-3192
Re: THE APPLICATION OF BP ) Conservation Order No. 275 EXPLORATION (ALASKA) ) INC. for classification of new ) Endicott Field oil pools and prescribing pool ) Ivishak Oil Pool rules for development in the ) Alapah Oil Pool Duck Island Unit of the ) Endicott Field. ) April 24, 1991
IT APPEARING THAT:
1. BP Exploration (Alaska) Inc. submitted an application dated January 11, 1991 requesting a public hearing for the establishment of pool rules for the development and exploitation of the Sag Delta North oil accumulation.
2. Notice of public hearing to be held March 12, 1991 was published in the Anchorage Daily News and the Anchorage Times on February 6, 1991.
3. A hearing covering the matter of the applicant's request was held in conformance with 20 AAC 25.540 at the office of the Commission, 3001 Porcupine Drive, Anchorage, Alaska 99501 at 9:00 a. m. on March 12, 1991.
4. Members on the staff of BP Exploration (Alaska) Inc. presented testimony including exhibits. The hearing record was closed at the end of the public hearing.
1. Hydrocarbons are trapped in the Ivishak Formation, a member of the Sadlerochit Group, and the Alapah Formation, a member of the Lisburne Group within Tracts 13 and 15 of the Duck Island Unit.
2. The Ivishak and Alapah oil accumulations appear to be separate based on pressure measurements and oil gravities. Oil gravity is 25° API in the Ivishak compared to 28° to 29° API in the Alapah.
3. The accumulations encompass an area of approximately 380 acres and are characterized by wells Sag Delta No. 9 (SD-9), Sag Delta North No. 1 (SNO-1), Sag Delta North No. 2 (SNO-2), and Sag Delta North No. 3 (SNO-3).
4. The vertical limits of the pools may be defined by the accumulations in the BP Exploration SD-9 well which appears to be a typical and representative well.
5. Well control and 3-D seismic coverage are adequate to reasonably define the areal limits of the accumulations.
6. The pools are bounded to the south by a major fault and there appear to be numerous smaller faults within the accumulations.
7. The base of the Ivishak light oil column appears to be planar and occurs at 10,112 feet measured depth in the SNO-2 well. It is underlain by a tar mat, which separates an aquifer from the oil column. Data show the tar mat will transmit pressure but appears to be immobile.
8. The Alapah appears to have multiple oil/water contacts based on petrophysical calculations.
9. Volumetric calculations of original oil in place indicate approximately 14 million stock tank barrels (STB) in the Ivishak and approximately 3.7 million STB in the Alapah.
10. Initial Ivishak reservoir pressure is 4825 psig and temperature is 212°F at 10,000 feet true vertical depth.
11. Reservoir performance testing began at SD-9 on July 31, 1989 to gather data for development and depletion planning. Wells SNO-3, SNO-1 and SNO-2 were drilled and put on production in September 1990, November 1990, and December 1990, respectively.
12. The SD-9 well watered out in February, 1991, after producing approximately 1.5 million STB of oil.
13. SD-9 was converted to water injection in March 1991.
14. The SNO-1, SNO-2 and SNO-3 wells are currently on production.
15. At least two well tests per month per well are being conducted for allocation purposes.
16. Development of the Ivishak and Alapah accumulations is predicated on facilities sharing and commingling production with the Endicott Oil Pool production located on the Main Production Island (MPI).
17. Primary depletion mechanisms indicated by test performance are solution gas drive and partial water drive in the Ivishak sands. Primary recovery is estimated to be 30% of original oil in place.
18. Predictive studies indicate waterflooding the Ivishak reservoir will increase recoveries to 35-44% of original oil in place.
19. An Alapah zone was tested in SNO-3 and rapidly depleted during a test period of 24 days. Total recovery is estimated to be 200,000 STB from the Alapah.
20. Commingling Alapah and Ivishak production within the same wellbore will be a way to capture Alapah reserves which would not be developed separately.
21. The SNO-1, SNO-2 and SNO-3 wells were completed such that the Alapah and Ivishak intervals can be isolated from each other.
22. Drilling units of 40 acres will be adequate to efficiently develop the small, irregularly shaped and faulted blocks making up the Ivishak and Alapah accumulations.
23. No evidence for a gas cap in either pool has been indicated.
24. A Sag Delta North Participating Area has been established by the owner/operator which encompasses the Ivishak and Alapah oil accumulations and has been submitted to the Department of Natural Resources for approval.
25. Wells drilled from the Main Production Island (MPI) of the Duck Island Unit, Endicott Field, are not required to have conductor casing (CO216).
26. A waiver of the diverter system required by 20 AAC 25.035(b)(1) has been granted for all Duck Island Unit, Endicott Field wells.
27. Waivers of the requirements for formation leak-off tests below structural and intermediate casing have been granted all Duck Island Unit, Endicott Field wells.
1. Establishing pool rules for the hydrocarbon accumulations in the Ivishak and Alapah formations occurring within the boundaries of the Duck Island Unit, Endicott Field, is appropriate.
2. Forty(40)-acre drilling units provide necessary flexibility to locate wells for efficient development of the irregular shaped and faulted Ivishak and Alapah oil accumulations.
3. Surface commingling of production from the Ivishak and Alapah accumulations with production from the Endicott Oil Pool is necessary.
4. Downhole commingling of production from the Ivishak and Alapah accumulations is necessary and will allow recovery of reserves in the Alapah which might otherwise not be produced.
5. A full scale waterflood in the Ivishak accumulation to replace voidage will increase ultimate recovery.
NOW, THEREFORE IT IS ORDERED THAT the rules hereinafter set forth apply to the following described area of the Duck Island Unit, Endicott Field, referred to in this order as the affected area:
T12N R16E Section 25 NE¼
Section 24: All state lands within the E½
T12N R17E Section 19 All state lands
Section 20 All state lands
Section 29 All state lands within the N½
Section 30 N½
Rule 1 FIELD AND POOL NAME.
The hydrocarbons contained within the Ivishak and Alapah Formations constitute reservoirs named the Ivishak Oil Pool and Alapah Oil Pool respectively. Their development areas are within the Duck Island Unit, Endicott Field.
Rule 2 POOL DEFINITION.
The Ivishak Oil Pool is defined as the accumulation of hydrocarbons that are common to and which correlate with the accumulation in the BP Exploration Sag Delta No. 9 well between the measured depths of 12069 and 12314 feet. The Alapah Oil Pool is defined as the accumulation of hydrocarbons that are common to and which correlate with the accumulation in the BP Exploration Sag Delta No. 9 well between the measured depths of 12418 and 12992 feet.
Rule 3 WELL SPACING.
(a) Nominal 40-acre drilling units are established for the pool within the affected area. Each drilling unit shall conform to quarter-governmental sections as projected. No more than one well may be drilled into and produced from each drilling unit. The pool may not be opened in a well closer than 1000 feet to any well opened to a common pool. Neither pool shall be opened in any well closer than 500 feet to the exterior boundary of the affected area.
(b) The Commission may administratively approve modifications to well spacing when justified.
Rule 4 CASING AND CEMENTING REQUIREMENTS
(a) Surface casing, to provide for proper anchorage, for preventing uncontrolled flow and to protect the well from the effects of permafrost thaw-subsidence or freeze-back loadings, shall be set at least 500 measured feet below the base of the ice-bearing permafrost. Sufficient cement shall be used to fill the annulus behind the casing to at least the mud line.
(b) Alternate means for maintaining the integrity of the well from the effects of permafrost thaw-subsidence and freeze-back may be administratively approved by the Commission upon application and presentation of data which show the alternatives are appropriate, based upon accepted engineering principles.
(c) Conductor casing is not required.
(d) Formation leak-off tests are not required below structural and intermediate casing.
Rule 5 DIVERTER SYSTEM
A diverter system is not required on the structural casing.
Rule 6 COMPLETION PRACTICES
(a) Wells completed for production or injection in the Sag Delta North Participating Area may utilize casing strings or liners cemented through the productive intervals and perforated, slotted liners, screen wrapped liners or open hole methods, or combination thereof. The Commission may administratively approve alternate completion methods where appropriate.
(b) Wells completed with the ability to have both Ivishak and Alapah Pools open to the same wellbore must have a means of isolating one from the other to prevent crossflow. Means to isolate the zones may include but are not limited to packer tailpipe assemblies, through tubing bridge plugs, cement squeezing, and cement plugging. The Commission may administratively approve alternate isolation methods where appropriate.
Rule 7 PRESSURE SURVEYS
(a) Prior to regular production, a pressure survey shall be taken on each well.
(b) The datum for all pressure surveys is 10,000 feet subsea.
(c) A minimum of one bottom-hole pressure survey per producing governmental section shall be run annually. The survey in part (a) of this rule may be used to fulfill the minimum requirements.
(d) Pressure survey, as used in this rule may mean a static bottom-hole pressure survey, pressure transient survey, or open hole pressure tests such as repeat formation tests and drill stem pressure tests.
(e) Data from all pressure surveys shall be filed with the Commission on Form 10-412 within 45 days after the survey is taken.
Rule 8 POOL-WIDE WATERFLOOD PROJECT
(a) A waterflood project is approved for the Ivishak Pool.
(b) Wells SD-9 and SNO-4 are approved as water injection wells in the Ivishak Pool.
(c) The Commission may approve additional wells as water injectors upon written application.
(d) Annual fluid withdrawal from the Ivishak Pool shall not exceed annual fluid injection by more than 10%.
Rule 9 GAS-OIL RATIO EXEMPTION
Wells producing from the Ivishak and Alapah Oil Pools are exempt from the gas-oil ratio limits set forth in 20 AAC 25.240(b).
Rule 10 COMMON PRODUCTION FACILITIES AND COMMINGLING
(a) Production from the Ivishak Pool and Alapah Pool may be commingled in the wellbore. Appropriate production logs shall be run to determine proper allocation of produced fluids with results reported to the Commission.
(b) Production from the Ivishak Pool and Alapah Pool may be commingled on the surface with production from the Endicott Oil Pool prior to custody transfer.
(c) Each producing well completed in the Ivishak and/or Alapah Pool shall be tested at least twice a month for a minimum of four hours at a stabilized flow rate.
(d) The Commission may require more frequent or longer well tests if the summation of the calculated monthly production volume for all pools is not within 10% of the actual LACT metered volume.
(e) The operator shall provide the Commission with a well test and allocation report at the end of each calendar year. The report will consist of a thorough analysis of all surveillance data relative to the well test system and the resulting allocation factors.
Rule 11 GAS OFFTAKE
(a) Gas produced from the Sag Delta North Participating Area may be utilized as fuel in the Endicott Field facilities.
(b) Gas produced from the Sag Delta North Participating Area not utilized as fuel will be injected into the Endicott Pool gas cap.
Rule 12 ADMINISTRATIVE ACTION
On its own motion or upon written request, the Commission may administratively amend this order so long as the change does not promote waste, jeopardize correlative rights, and is based on sound engineering principles.
DONE at Anchorage, Alaska and dated April 24, 1991.
David W. Johnston, Chairman
Alaska Oil and Gas Conservation Commission
Lonnie C. Smith, Commissioner
Alaska Oil and Gas Conservation Commission
Russell A. Douglass, Commissioner
Alaska Oil and Gas Conservation Commission