A Practical Approach to Drilling-Fluid Surveillance and Management
- M.A. McLane (Exxon Co. U.S.A.) | G.H. Medley Jr. (Exxon Co. U.S.A.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- December 1993
- Document Type
- Journal Paper
- 277 - 282
- 1993. Society of Petroleum Engineers
- 1.7.7 Cuttings Transport, 1.6 Drilling Operations, 5.1.2 Faults and Fracture Characterisation, 4.3.1 Hydrates, 1.6.9 Coring, Fishing, 1.11 Drilling Fluids and Materials, 4.2 Pipelines, Flowlines and Risers, 1.6.1 Drilling Operation Management, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.11.4 Solids Control
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Since the mid 1980's, Exxon Company, U.S.A.'s Midland Drilling Organization has used Low Solids-Polymer Extended (LSPE) drilling fluids extensively in its Rocky Mountain Operations. These muds, when combined with good surveillance and management, have contributed to significant improvements in drilling performance and cost reductions.
This paper summarizes Exxon's experience with LSPE muds and describes surveillance techniques that have been developed to optimize drilling performance. It also reviews guidelines for maintaining these muds and discusses limitations on their use. Case histories from three Wyoming field areas are included to provide background data. These field data are used to describe the evolution of LSPE mud surveillance tools and to illustrate the benefits of using the LSPE system. Potential problems that may occur when using these muds are also discussed.
Between 35% and 40% of all wells drilled in the Rocky Mountains since 1986 by Exxon have been drilled using Low Solids-Polymer Extended (LSPE) muds, also referred to as Low Solids, Non-Dispersed (LSND) muds and as partially hydrolyzed polyacrylamide (PHPA) muds. Before that time less than 10% of Exxon's wells in the region were drilled with similar systems. Prior to the mid-1980's the predominate mud used by Exxon was a Fresh Water Gel/Lignosulfonate system, although many other systems were also used. The switch to LSPE muds was made in an attempt to solve some of the problems common to Rocky Mountain drilling, or at least to minimize the symptoms of these problems.
Wellbore instability is a major problem in several basins in the Rocky Mountains. This instability can be caused by shales, coal s or other hydratable formations sloughing and is exacerbated by an inability to properly clean the hole. Secondary problems that often result include high torque and drag, stuck pipe and stuck logging tools. Other problems include low rate of penetration (ROP) caused, in part, by the hard rock and lost penetration (ROP) caused, in part, by the hard rock and lost returns zones found in at least one segment of nearly every well drilled in the Rockies. Increasing concern for the environment and the attendant regulatory requirements are another major driver of the decision on what type of drilling fluid system to use.
LSPE muds help alleviate all these problems. Exxon's approach in the Rockies has been to concentrate less on shale stabilization and inhibition of clays and more on removal of clays before dispersion. Hole cleaning is improved by the rheological properties exhibited by these muds. However, use of a LSPE mud in regions with extremely hydratable shales with thick intervals of highly bentonitic formations (i.e. "mud making" formations) have not responded well to use of a LSPE mud, especially when those formations have been exposed in the wellbore for long periods of time. Torque and drag can be decreased with the use of LSPE muds, in part because of the natural lubricity of the PHPA polymers, but also because of the more efficient removal of polymers, but also because of the more efficient removal of cuttings where lack of hole cleaning contributes to drag.
The increased ROPs experienced with LSPE muds help with the instability problem simply by avoiding the symptoms. Since the wells are drilled faster, the trouble formations are often not exposed long enough to cause problems.
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