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ARCO Alaska details enhanced oil recovery plans for Alpine Miscible water-alternating-gas EOR proposed from startup estimated to recover 45 percent of original oil in place Kristen Nelson PNA News Editor
ARCO Alaska Inc. has requested a hearing before the Alaska Oil and Gas Conservation Commission on or after Oct. 12 to present its plans for miscible water-alternating-gas enhanced oil recovery at the Alpine field west of Kuparuk.
The commission held an Alpine field development hearing in December and issued pool rules in March. At that hearing, ARCO Alaska officials told the company that while they were presenting the original plan of development for the field, they were working on approval for a new plan of development.
The original plan for the field called for horizontal wells in the center and vertical wells at the edges. Horizontal wells were to be on 275 acre spacing and vertical wells on 160 acre spacing with waterflood in the center of the field and gas re-injection around the edges. Estimated recovery with the original plan was 38 percent of original oil in place.
In a plan submitted in early September, ARCO told the state that the new development plan includes only horizontal wells on 135 acre spacing with a miscible water-alternating-gas enhanced oil recovery process implemented at startup. The miscible injectant will be made from solution gas enriched with components recovered from the fuel gas. The new plan of development is estimated to recover 45 percent of the original oil in place, 429 million barrels of an estimated 960 million barrels of oil in place, an improvement of approximately 11 percent compared to estimates that the original plan of development would recover approximately 329 million barrels.
3,000-foot horizontal sections Development of the field will still be from two drill sites, but the new plan includes only horizontal wells. Rows of injectors and producers will be spaced 1,500 feet apart. The wells will have 3,000-foot horizontal sections with 1,000 feet of lateral displacement between wells along each row.
ARCO told regulators that flow studies indicate the waterflood process at Alpine will leave behind “high residual oil saturations” of 35-40 percent, providing “an excellent tertiary recovery target.”
Gas separated from the oil at Alpine will be enriched with components from fuel gas. ARCO said it will be important to start miscible water-alternating-gas recovery at startup at the Alpine field. Models of recovery at Alpine indicate that miscible water-alternating-gas EOR could increase individual pattern recoveries by 10-12 percent of original oil in place over waterflooding.
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