Abstract

Development drilling of the Mississippi Limestone in southwestern Garfield County, Oklahoma, took place in the mid-1960's. Most of the development was either one well per quarter-section or one well per section, depending on the predominance of oil or gas in the hydrocarbon production.

In 1972, Union Texas Petroleum Division, Allied Chemical Corporation, drilled a second well on one of the quarter-sections to test the adequacy of the drainage by the original well. Results indicated that additional development was justified, and numerous new wells have been drilled since that time by Union Texas and by other operators as well. Drilling problems, completion techniques and some of the problems, completion techniques and some of the results obtained are discussed.

Introduction

The Mississippi Limestone is a massive fractured limestone underlying a large part of northwestern Oklahoma. It has been found productive of hydrocarbons in varying degrees productive of hydrocarbons in varying degrees over much of an area stretching from 12 miles east of Enid to 40 miles west and from 12 miles north to 15 miles south, give or take a few miles in any direction.

The specific part of this area to be discussed is north and west of the town of Waukomis, mostly in Township 21 North, Range 7 West. Most of this township had been developed in the mid-1960's with only one well per quarter-section, thought at the time to per quarter-section, thought at the time to be sufficient to recover the hydrocarbons which were economically recoverable. Some of the sections in the northern part of T21N and all of those in T22N had only one well per section, because they had been predominantly gas productive when completed. In 1972 the Exploration Department of Union Texas Petroleum prepared several maps contoured on Petroleum prepared several maps contoured on cumulative oil production through June 1971. The map of the Waukomis area indicated that the wells in T21N, R7W had recovered significantly more oil than in other areas, as shown in Figure 1.

The Mississippi Limestone has very low porosity, generally in the 3 - 6% range. porosity, generally in the 3 - 6% range. At the same time, this porosity is present throughout the entire thickness, which exceeds 500' in most of the wells.

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