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BP Exploration to begin water flood at Eider Small pool at Endicott unit expected to produce 5 million barrels over next 10 years from 13.2 million barrels of oil in place Kristen Nelson PNA News Editor
The Alaska Oil and Gas Conservation Commission approved water flood at the Eider pool in the Endicott field June 2, responding to a request by BP Exploration (Alaska) Inc. at a May 25 hearing for an expedited ruling on that portion of a pool rules and water flood application.
Company officials asked commissioners Dan Seamount and Camille Oechsli Taylor at the hearing to allow water flood prior to issuance of an injection order, saying that a commercial agreement with other Endicott owners was imminent. The commission said that an order would be required and agreed to expedite issuance of that order.
On the pool rules portion of the application, commission staff asked BP Exploration (Alaska) officials why the proposed pool did not include the Sag River formation above the Ivishak, as was done at Prudhoe Bay. BP officials said that the Sag River sandstone is non-productive at Eider and was not included in the Eider participating area previously approved by the Department of Natural Resources Division of Oil and Gas.
As defined by the commission, a pool includes formations in pressure communication. While pressure communication is indeterminate between the Sag River and Ivishak, Bob Crandall, commission senior petroleum geologist argued, it is at least as likely that they are in communication as that they aren’t, and should be included. BP representatives at the hearing said the company was willing to have Sag included in the pool.
Eider discovered in 1998 BP said the Eider field was discovered in 1998 underlying state leases some one and one-half miles offshore. The hydrocarbon-bearing zones cover an area of approximately 300 acres.
There are seven reservoir penetrations at the field: two completed wells, Eider 1 (2-56A/EI01) and Eider 2 (2-30A/EI02) and five additional sidetracks or plug backs (2-56/EI-01, 2-56A/PB1, 2-56A/PB2, 2-30A/PB1 and 2-30A/PB2).
BP said hydrocarbons in the Eider field are trapped in sandstones and conglomerates of the Ivishak formation, correlative to Prudhoe Bay Ivishak Zone 2 and to Sag Delta North Ivishak. The Eider formation has been subdivided into an upper sand, a middle shale containing a sandstone unit and a lower sand, similar to the Sag Delta North field.
Total original oil in place is 13.2 million barrels with a gas cap estimated at 33 billion standard cubic feet. BP noted that this figure is down from the 18 million barrels of oil in place originally estimated because the field was found to contain fewer hydrocarbons than originally estimated.
BP described the field as a fault-controlled anticlinal structure truncated at the top by the Lower Cretaceous unconformity, with hydrocarbons reservoired in the Triassic Ivishak formation. There are three major fault blocks in the field. BP said there is a fair-to-good seismic data set in the area of the Eider field and that major bounding faults are clearly resolved and considered to be accurately located.
Production from lower sand Both existing wells produce from the lower sand only, 1 Eider from the central fault block and 2 Eider from both the central and western fault blocks.
BP said a full-field reservoir simulation model was developed to study field performance and develop a depletion plan to maximize economic recovery. Primary depletion, water injection and gas injection were investigated and voidage replacement with water injection was considered to be the most beneficial and efficient approach to enhanced recovery.
BP said the more than 5 million barrels are expected to be produced within the next 10 years using water injection. The company said reservoir simulation shows an expected incremental increase in ultimate recovery of 1.5 million to 3 million barrels as a result of proposed water injection into 2-56A/EI01.
Recovery from primary depletion is estimated at 15 percent; with water injection, recovery is estimated at 27-38 percent.
The company said that initial production will begin when water flood is implemented with an expected initial rate of 1,500 barrels of oil per day. Maximum water injection rates are expected to range from 15,000 to 20,000 barrels of water per day. BP said that water injection will then match voidage.
Initial production will be from the lower sand unit, which BP said holds the largest single amount of reserves.
BP said no further drilling is planned at this time, although this decision will be reviewed at the pool matures and more information is gathered.
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