Abstract

The Viola limestone has become one of the major exploration objectives in southern Oklahoma. A number of fields have been discovered along the northern flank of the Marietta Basin in the past five years, and Viola exploration continues to expand along this trend.

Southeast Joiner City Field, located in Carter and Love Counties, Oklahoma, has been an area of recent Viola activity. Structurally, it is a NW-SE trending anticline, bounded on the southwest by a small reverse fault, and on the northeast by the southern limb of the Rock Creek Nose.

In July, 1979, Chevron U.S.A. deepened the J.S. Bates et al #1 to the Viola and completed the well for an IP of 654 BOPD. A total of eleven Viola wells have since been completed in Southeast Joiner City Field by Chevron, and one additional well by Petro-Lewis. Total field production from the Viola as of November 9, 1980, was 266,039 barrels.

The Viola limestone in Southeast Joiner City can be divided into three units, based upon log character and sample description. The upper unit, 450 feet thick, is composed of very fine to microcrystalline, dense limestone, tan to brown to grayish brown in color. The middle unit, approximately 150 feet thick, is characteristically an argillaceous limestone. The lower unit, 450 feet thick, is similar to the upper Viola unit, but is characterized by an increase in siliceous limestone with depth. The lowermost 100 to 130 feet of the lower Viola is predominantly dark brown to black, microcrystalline, highly siliceous limestone. Well-cuttings from this section commonly contain abundant evidence of fracturing. Low matrix porosity through the entire section, combined with the lack of correlation between well potential and structural position, indicates that production is related to fracture porosity. A number of methods have been used to predict or identify fracturing, including both dipmeter and acoustic velocity related fracture logs.