Operational Problems in North Burbank Unit Surfactant/Polymer Project (1980)

The North Burbank pilot project is being conducted to determine the feasibility of a surfactant/polymer project that involves injecting a series of chemical solutions: freshwater preflush, salt-water preflush, surfactant, and polymer. This paper discusses operational problems encountered in each stage and describes alternative approaches used to minimize adverse effects on overall performance. Introduction In 1975, Phillips Petroleum Co. initiated a pilot project to demonstrate the feasibility of applying a surfactant/ polymer flood to an oil-wet sandstone reservoir that was polymer flood to an oil-wet sandstone reservoir that was nearing the end of its producing life. This paper describes, in order of the chemical injection phases, the chemicals used in the surfactant/polymer process, the mechanical system constructed to mix and inject the chemicals, the operating procedures developed, and the problems encountered. The North Burbank Unit (Fig. 1), located in Osage County, OK, has been producing under waterflood since 1950. Discovered in 1920, the unit produces a sweet 39 degrees API (828-kg/m3) gravity oil from the Burbank sand-stone, a well-consolidated sand lens averaging 47 ft (14.3 m) thick at depths of 2,700 to 2,900 ft (823 to 884 m) and covering about 24,500 acres (9914.8 m2). As of Aug. 1979, the North Burbank Unit (NBU) had yielded 299,400,000 bbl (476 Mm 3) of oil, through primary and secondary recovery, out of an estimated 671,300,000 bbl (1070 Mm3) of oil originally in place, Oil production has declined to the point that the unit is classified as stripper production. As operator of NBU and under contract to the production. As operator of NBU and under contract to the U.S. ERDA (now DOE), Phillips developed a 90-acre (36.4-m2) pilot project to test the feasibility of applying a pilot project to test the feasibility of applying a surfactant/polymer flood to the unit to extend the producing life and increase ultimate oil recovery. producing life and increase ultimate oil recovery. General Field Operations: NBU Tract 97 The pilot project being conducted at NBU Tract 97 (Fig. 2) has been operating since Oct. 1975. The well pattern consists of nine 10-acre (4.05-m2) inverted five spots with an injection well surrounded by four producing wells. In the waterflood operations carried on at NBU, the oil wells produce at an average water/oil ratio of 97. The produced produce at an average water/oil ratio of 97. The produced fluid is transferred from the wells through a gathering system to one of several tank batteries for separation and LACT sales. A small amount of fresh water is mixed with the produced salt water to make up the injection volume produced salt water to make up the injection volume requirements and is injected back into the Burbank sand. In the pilot project being conducted at NBU Tract 97, the injection fluid for a period of 27 months consisted of a specially designed series of chemical solutions (Fig. 3).The production and injection fluids for NBU Tract 97 are handled at a tank battery (Fig. 4) and a water station (Fig. 5) located at Tract 97. These facilities were redesigned so that the production and injection fluids for Tract 97 would be isolated from the fluids for the other tracts.To form the inverted five-spot well pattern, 11 new producers and nine new injectors were drilled in 1975. producers and nine new injectors were drilled in 1975. The new producers have 7-in. (177.8-mm) OD casing set into the top of the Burbank and were completed with 2 1/2-in. (63.5-mm) sucker rod pumps and 3 1/2-in. (88. 9mm) OD EUE tubing set at 2,600 ft (792,5-m). The old producers used multiple casing strings with 5 1/2-in. producers used multiple casing strings with 5 1/2-in. (139.7-mm) OD liners set into the top of the Burbank. All producers were completed as open holes. JPT P. 11