First Prediction and Practical Techniques for HPHT Drilling 1950-1980

Rehm, William A. (Retired)


This paper revisits advancements in drilling high-temperature and high-pressure wells during the period 1950-1980. It was during this period that many of the planning and drilling techniques in use today were first identified, and in many cases, resolved on the drilling rig. The paper is drawn from personal recollections and published material, with particular emphasis on contributions from operator and service-company personnel at the rig site in the Gulf of Mexico and Gulf Coast basin. 1950 was a time when well kicks were "controlled?? on a local basis with whatever seemed to work, generally the constant annulus pressure or constant pit volume methods. Many of the well flows, fortunately, were saturated salt water and less hazardous than gas. Fracture gradient was an unknown value and stuck pipe and lost circulation seemingly occurred by happenstance. Mud solidification was similarly dealt with on a local basis with dilution of incorporated native solids and/or the addition of more dispersant in water-based muds. This also reinforced the importance of the high lime mud's ability to tolerate contamination.
The paper serves to highlight how resourceful field personnel working in concert with innovative staff engineers can achieve extraordinary success. This was and is especially critical in an industry fraught with uncertainty.

In 1950, the drilling industry had little idea of how to predict geopressures, a term coined by Charles Stuart,48, and even less of an idea of how to deal with High-Temperature, High-Pressure (HTHP) wells. The initial development of technology adequate to economically drill HTHP wells was piecemeal and by trial and error. Theory often followed practice. During the period 1950-1980, while there were some very notable exceptions, more typical deep well temperatures started to approach 300 °F and pressures approached 15,000 psi.
Geological papers published from the 1920's to the 1960's discussed earth temperatures and pressures from an academic viewpoint, 1,10,32,47,48,49 , but their value was not fully recognized until they were compiled with developing drilling technology in the late 1970's.
Higher temperatures and higher pressures required better drilling fluids leading to a progression from phosphate muds to high-lime, low-lime, gypsum, and lignosulfonate drilling fluids with 10% diesel oil that were more resistant to the conditions in the HTHP wells. At the same time, "true?? oil-based drilling fluids gave way to invert emulsions that ultimately resolved many of the problems with wellbore stability.
A landmark paper on well control methods by Obrien and Goins 38 opened the door to more discussion about predicting wellbore pressures instead of just reacting to them. The key thoughts about pressure caps and transition zones led to major breakthroughs in pressure prediction.
Mobile computing devices did not exist then, but special slide rules and nomographs were developed by different service companies to allow application of some of these techniques at the wellsite. By 1980, most of the new geopressured operating techniques were accepted as basic standards for HTHP drilling, and industry was starting incorporate predictive and operating procedures into computers that were becoming commonplace and readily available.