A Computerized File for Directional Well Courses

Abstract

When the job is to drill blindly through a mess of spaghetti, it's hard to avoid a collision. In the Huntington Beach Offshore field of California, the computer has been used successfully as a seeing-eye dog. Introduction The Huntington Beach Offshore field, Orange County, Calif., is one of the nation's larger oil fields. Two unusual features are the complex faulting and the extreme thickness of the productive zones (one is more than 900 ft in gross section. Although there are two platforms located within the 3-mile limit, most of the platforms located within the 3-mile limit, most of the field has been developed from shore with high-angle wells (as high as 80 degrees from vertical). The rows of pumping jacks are so closely spaced that they have pumping jacks are so closely spaced that they have become a tourist attraction. Secondary recovery has given this field, discovered in 1931, a new lease on life. Waterflooding is the predominant mechanism, with injection rates expected predominant mechanism, with injection rates expected to exceed 1 million B/D by 1972. Steam stimulation is also being applied in the upper, low-gravity-oil zones. Early in the life of the first full-scale waterflood it became obvious that the complex geology played a dominant role. A new and complete geological study to find even the small displacement faults was vitally necessary. To obtain effective sand control for successful secondary recovery, it would also be necessary to redrill nearly every well. Strict well-course control was required to build up to 75 degrees for horizontal distance, to drop to 45 degrees for efficient gravel-packing, to avoid excessive doglegs and to prevent collisions. These urgent needs and the large amount of data from the 1,200 wells made this a natural project for computerization. We shall describe here the way we did this and the results we obtained. Planning the File Planning the File The program was divided into two basic phases. In the first phase the raw data from the directional surveys and geological markers were entered on punch cards, the data were verified, and the surveys were recomputed as accurately as appeared reasonable. The tangential method, with both drift and direction angles average, was chosen as the most accurate, practical calculation procedure. The second phase practical calculation procedure. The second phase included building the master tape file and developing the software for graphical displays of maps and cross-sections. Had a problem developed in Phase II, the completion of Phase I would still have been economically justified. Uses of the File The following are the principal ways in which the file is used:to make books from the survey printouts,to prepare geological cross-sections,to prepare geological subsurface maps,to make master maps of the well courses,to search a given course for all interference wells, andto plot well courses in plan or section. plan or section. The books that contain the surveys are very popular because they provide the most accessible, popular because they provide the most accessible, up-to-date source of the well status. Many of these wells have been redrilled a number of times because the liner failed and lost control of the sand. JPT P. 267