Increasing Injectivity of Shaly Sands With Chemicals

Abstract

CHAKRAVORTY, S.K., HUDSON'S BAY OIL and GAS CO., LTD., CALGARY, ALTA. GATEMAN, J.C., HUDSON'S BAY OIL and GAS CO., LTD., CALGARY, ALTA. MEMBERS AIME BOHOR, B.F., CONTINENTAL OIL CO., PONCA CITY, OKLA. KNUTSON, C.F., CONTINENTAL OIL CO., PONCA CITY, OKLA. Abstract The Viking sandstone reservoir, Coleville-Smiley field, Saskatchewan, Canada, is very shaly and water sensitive. The proven sources of injection water in the area are relatively fresh and in laboratory tests quickly plug tile Viking cores. After screening a large number of chemicals in the laboratory, a two-stage treatment was developed that maximized water permeabilities in core plugs. The purpose of the treatment was to restrict or inhibit clay swelling, prevent bacterial growth and increase injectivity. No one chemical was found that could do all these jobs well, so a three-component system was used: potassium chloride, polyoxyethylene triethylenediamine and an imidazoline. The optimum laboratory technique was to use a spearhead containing a high concentration of the treating chemicals followed by continuous treatment of the injection water with these material. Introduction The Eureka Viking sand pool is located in Southeastern Saskatchewan, about 200 miles northwest of Regina, 50 miles east of the Alberta-Saskatchewan border, and 200 miles north of the International Boundary (Fig. 1). The pool is located on the western end of the Dodsland field and is approximately 15 miles east of the Smiley-Dewar Viking sand pool. These two pools are within the Coleville-Smiley field boundaries as defined by the Saskatchewan Dept. of Mineral Resources. The producing formation of these pools is the Viking sandstone found at a depth of approximately 2,300 ft. The discussion presented in this paper pertains only to the Viking formation. Production was first established from the Viking sandstone in this area in Sept., 1953, with the discovery of the Smiley-Dewar pool. Discovery of the Eureka pool followed in 1954 and production was established for the Dodsland field in 1958. These fields presently contain approximately 650 wells capable of production from the Viking sandstone. The Viking sand is continuous throughout this area and the oil is found in the lows or valleys of the structure. Gas caps are located between the Eureka and Smiley-Dewar pools and along the northern edge of the Dodsland field. The name and location of the well selected for the injectivity test is HB Coleville 4-26-31-23 (lsd 4-26-3 1-23 W3M) in the Eureka Viking sand pool (Fig. 2). Other pilot water injection wells are located in lsds 11-6-31-22 W3M, and 12-7-31-20 W3M in the Dodsland field, lsd 9-4-31-25 W3M, and a four-well five-spot pilot injection on section 17-31-25 W3M in the Smiley-Dewar pool. Geology and Reservoir Characteristics The Viking member of the Colorado formation is of lower Cretaceous age. It consists of gray, silty shale beds and thin beds of chert pebbles. The lower 30 ft of the Viking member, consisting of medium-grained shaly sand, is known as the Viking sandstone. Structurally, the Viking member reflects the Paleozoic erosional surface by its highs and lows. JPT P. 1107ˆ