A review of treatment designs and resulting productivity of wells completed by other operators found that small proppant volumes (<50,000 lbs) and low pumping concentrations (< 4 ppg) contributed to ineffective fracture conductivity and low apparent frac lengths. Redesigned treatments successfully placed large volumes of HSP at concentrations up to 7 ppg. These new wells have outperformed offset wells despite significantly depleted reservoir pressures.
Late in the fall of 2000 a concerted effort was initiated to optimize fracture stimulation of the Deep Morrow Sandstone in Mayfield area of Western Oklahoma. The producing horizons, typically four or more stacked pays, in the Mayfield area are from 17,000 to 20,500 feet and exhibit extreme heterogeneity including tremendous variations in permeability, pressure, and aerial extent of the reservoir. The presence of severe depletion in some of the zones greatly complicates completion techniques.
The initial approach was to utilize pressure data from previous treatments in the field and attempt to gain qualitative values for stress profiles. Based upon this data available a procedure was developed to optimize stimulation treatments using an iterative process. The use of pre-job FET's allowed evaluation of fluid efficiency and also to identify severe tortuosity problems.
The use of field proven techniques used in other deep high temperature reservoirs allowed for removal of severe near-wellbore problems allowing for placement of up to 7 pound per gallon bauxite in wells below 20,000 feet. The authors will elucidate the step- by-step procedures utilized in selection of pad volume, leak-off control methods, and specific procedures for removal of tortuosity. Additionally we will discuss the success and failures of zonal isolation techniques and the successful use of pseudo-limited entry on some of the producing horizons.
The new procedure allowed for successful placement of higher concentration of proppant and much larger volumes of proppant.
A major part of the paper will be comparing the new-generation treatment results to offset operators and comparison of production data on a well-to-well basis.
Author(s): John W. Ely, Ely and Associates, Inc.; Michael A. Martin, BJ Services Company, U.S.A.; Jose J. Duenas, Jerry R. Trythall, BP America Production Company
Paper Number: SPE 80932