Engineering and Planning a Deep Abnormally Pressured Well

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc. This paper was prepared for the 42nd Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Oct. 1–4, 1967. 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. The problems encountered in drilling deep abnormally pressured wells are generally known. Conclusions from a study of this subject were applied to design a deep well drilling program. More significant parts of the program are presented, excluding those parts already covered by previous published papers. Introduction Drilling deep wells which encounter abnormally pressured formations is an expensive venture and problems, such as stuck drill pipe, ruptured casing, lost circulation, gas kicks or salt water flows, may add greatly to this cost. Drilling practices that apply to shallow normally pressured wells are unsafe and inefficient beyond the high pressure transition of a deep well. As the strength limits of equipment, casing, and borehole rock are approached, every detail of drilling procedure becomes more critical. Judgments based on past experience alone are often in error without proper consideration of depth. Simple operations such as selecting proper mud weight and viscosity, pulling and running drill string and casing wear are major factors contributing to failure. It is not sufficient for the engineer to calculate force magnitude, design and present a well prognosis. The critical forces should be calculated then graphically demonstrated so that it can be easily and clearly understood. Once understanding is established, company and service personnel can be directed to the common objective. A meeting of all personnel directly responsible for drilling a well provides an excellent opportunity to discuss the program and establish communication. Coordination and communication are critical responsibilities of the drilling supervisor. INITIAL ENGINEERING AND PLANNING The starting point for any drilling plan is with the well location. Geological and seismic data are studied with particular attention to faulting. Logs and drilling records of all wells drilled around the proposed location are studied. Shale pore pressure and formation fracture gradient of wells are calculated and correlated in reference to the proposed location. Fig. 1 illustrates pore pressures and calculated formation fracture pressures of a South Louisiana well which penetrated deep into abnormally pressured formations.