Analysis of Pressure interference Tests Using Computer Graphics
Authors: Haynes R.D. , Sawyer W.K. 
Published: December 2007

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Computer graphics were used to analyze dynamic pressure responses from short-term interference tests that were conducted in an attempt to outline the natural and induced fracture systems in a petroleum reservoir. By use of a time-programmable data acquisition system, pressure responses from 40 wells arranged in 16 regular 5-spots were monitored during 74 water injection tests that resulted in over 120,000 individual pressure readings. To aid in the interpretation of the complex field behavior, the data were transferred to computer cards. Software was then developed using cathode ray tubes (CRT), drum plotter, and on-line printers to reduce and evaluate the data.

Pressure-time plots were generated for each well in a test. From these plots, tests that indicated evidence of existing fracture systems were selected for more detailed analysis. Of the selected tests, sequenced delta pressure contour maps were used to show the dynamic behavior of the field due to the interference test. Graphic three-dimensional perspective views of the changing field perspective views of the changing field pressures were also used in the interpretation pressures were also used in the interpretation of the reservoir behavior. Results of two specific tests are shown.

Introduction

A series of experiments was designed in an effort to map existing fracture systems in an oil reservoir. The delineation of natural and induced fractures in a petroleum reservoir is important in the determination of potential flow characteristics. Knowing these potential flow characteristics. Knowing these characteristics can result in a more efficient recovery of oil through the planning and operation of secondary and tertiary recovery projects.

A 36-acre test site owned and operated by the Minard Run Oil Company was selected near Bradford, Pa. The test site included 25 injection and 16 producer wells that had been fractured and used in a waterflooding operation. The spacing of the wells was arranged in 16 regular 5-spots and is shown in figure 1. The porosity of the producing formation averaged porosity of the producing formation averaged about 16 percent and had an average permeability of 6 millidarcys. The depth of the wells ranged from 1,950 to 2,000 feet.