Abstract

Exxon Company, U.S.A., is actively drilling deep Anadarko Basin wells in the development of its Northeast Mayfield Field in Beckham County, Oklahoma. Two wells have been drilled to date and a third and last one is drilling at the writing of this paper. The first well, Walne 1-34, drilled to a depth of 25,825" and was plugged back and completed in a limestone reservoir at 24,500". The second well, Hazel Howell 1-2, drilled to a depth of 25,565" and was also completed in the same limestone reservoir.

This paper presents a combined case history of the two wells mentioned above. In general, it briefly discusses both the geologic and drilling history of Northeast Mayfield and Exxon's basic drilling plans. Emphasis of the paper though, is focused plans. Emphasis of the paper though, is focused on actual drilling operations and results. Specific drilling practices developed for the area, including those related to safety and the environment, are outlined. In addition, detailed discussion is included on a number of unique occurrences and successful operations in the course of drilling both wells. These include:

  1. large nitrogen foamed cement jobs,

  2. extended nozzle insert bit usage,

  3. setting of a 5,800", 24 ppg pill at casing seat point,

  4. casing wear mitigation,

  5. deep underbalanced drilling and,

  6. a high pressure well control problem at 25,825".

In conclusion, the paper notes the key factors contributing to the success of these deep Anadarko Basin wells.

INTRODUCTION:

Exxon Company, U.S.A. began operating in Northeast Mayfield Field in 1988 after a purchase agreement was made with Leede Exploration. The field is located in the Anadarko Basin in western Oklahoma (Figure 1). Multiple hydrocarbon pay zones exist in the field, with the most significant one being the Middle Hunton. This reservoir was the primary objective of both wells discussed in this paper. The Arbuckle, a deeper, unexplored, prospective reservoir in the field, was a secondary objective. However, the Arbuckle was never penetrated in either well due to mechanical limitations and revised economic analysis.

Northeast Mayfield Field is located along the southern edge of the Anadarko Basin and is structurally comprised of a fault-bounded anticline. A geologic cross section of the basin, showing an approximate location of the field, is shown in Figure 2. Formation of the field is directly related to the Amarillo-Wichita uplift. This uplift is theorized to have resulted from compressive stresses transmitted far into the continental interior from plate tectonic activity. Complexly reverse faulted structures (i.e., anticlines) formed by this uplift, and combined with source beds, formed the basis for deep hydrocarbon traps. Subsidence of the basin is also thought to have occurred and erosion of the uplift filled in the basin, forming the shallow hydrocarbon traps. A carbonate sequence comprises most of the strata below 20,000", whereas the upper sections are mostly clastic in nature.

The Middle Hunton is a limestone reservoir at 24,500". Pore pressure is subnormal and the temperature is 380 degrees F. Gas production contains 1.5% H2S and 7.0% CO2 and is found in dolomitic streaks interspersed throughout the 800" thick limestone formation. Estimated ultimate recovery from the Middle Hunton is in excess of 200 BCF.

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