Ante Creek - A Miscible Flood Using Separator Gas and Water Injection

Abstract

The Ante Creek Beaverhill Lake pool in Alberta is a deep, high-pressure reservoir containing a light crude. A miscible flood, started in 1968, was designed on the basis of laboratory tests and utilizes the gas from the separator, alternating with water injection. The calculated recovery efficiency is 61 percent. Reservoir Description and Development The Ante Creek Beaverhill Lake oil pool located northwest of Edmonton was discovered in Nov., 1962, with the Atlantic Ante Creek 4–7 well. The producing horizon is the Swan Hills member of the Beaverhill Lake (BHL) formation at 11,000 ft depth. This formation is the same reef that is productive in the prolific Swan Hills oil fields and Kaybob South wet prolific Swan Hills oil fields and Kaybob South wet gas field (see Fig. 1). Ante Creek is the deepest of the Beaverhill Lake reservoirs discovered to date. The oil accumulation is found in the updip termination of a porous reefal development. There is a water line to the west side of the field. Cross-sections of the reservoir show that the porosity is scattered through the section but correlatable from well to well. There are presently 19 oil wells completed in the reservoir on 320-acre spacing. The interpreted isopachous map and material balance calculations indicate 37.5 million STB of oil in place. Table 1 lists the reservoir and fluid properties. Most notable of these properties are the low oil viscosity of 0.13 cp and the high initial pressure of 5,173 psia. Fig. 2 is a porosity-foot map of the pool, showing the unit outline. porosity-foot map of the pool, showing the unit outline. Secondary Recovery Considerations It was recognized early in the development of the reservoir that a pressure maintenance project would be advantageous. The reservoir pressure declined to 4,290 psia by Dec., 1966, approaching the bubble-point pressure of 4,140 psia. The primary recovery for the volatile oil was calculated to be 16.2 percent. Also a consideration for secondary recovery was the incentive offered by the Alberta proration system, whereby the well allowable is proportional to the recoverable reserves. With the level of primary reserves calculated for the pool the per-well allowable would drop to a minimum of 32 BOPD in 1969. In 1967 a depletion study was started, as was negotiation towards unitization. Since several other Beaverhill Lake fields in the province are under waterflood, with recoveries expected to be from 40 to 50 percent of the oil in place, waterflooding was considered here, also. However, several factors pointed toward miscible flooding: the high gravity of the oil, the high reservoir pressure, and the available casing-head gas. The gas from the field was being flared at rates of 2 to 3 million ft a day with no immediate prospects for sales. Following a review of the information available on miscible flooding and of the factors involved in operating a flood in Ante Creek, a method was developed to permit efficient oil recovery with the materials available. The method can be described as continuous alternate solvent water injection. P. 1232