Abstract

The PEM water-base polymer mud system was developed to provide an environmentally acceptable drilling fluid that approaches the inhibitive performance of an invert oil emulsion fluid.

PEM is engineered with a specially formulated PF-JLX additive for maximum shale inhibition and designed to drill high-angle wells in reactive formations, normally reserved for an oil-base mud. The primary functions of the PF-JLX in the system are to improve shale stability and the lubricity of the fluid.

Introduction

The PEM system can be engineered with potassium chloride, sodium chloride or other salts as the activator for the PF-JLX. For optimum performance, the PF-JLX concentration should be 3 to 5% by volume. The system is based on the solubility of the PF-JLX, which changes with the salinity and temperature of the fluid.

The biggest advantage of the PEM system is its engineering simplicity, requiring relatively few products. The fluid is designed around any basic polymer mud system, and the combined synergistic shale inhibition from PF-JLX and salt. The most common PEM systems are designed around the KCl/NaCl PF-PAC/PF-VIS system or the KCl/NaCl PF-PLUS system. The combined shale inhibition from PF-JLX, salt and polymers produces excellent shale inhibition compared to other water-base mud systems and makes the fluid a superior choice to drill troublesome shale.

The cloud-point phenomenon is believed to be the primary mechanism for stabilization with the PEM system. Maximum benefit is obtained when the PEM cloud point matches either the bottom-hole temperature or that of the exposed formation. Shale inhibition is improved when the PF-JLX is partially clouded out. This is based on the theory that once a shale is exposed to a mud containing soluble PF-JLX, the PF-JLX can invade microscopic shale pore throats where the change in chemical environment causes to cloud out. Once clouded, the PF-JLX blocks the shale pore throats, thus preventing further water invasion and the transmission of hydrostatic pressure (figure 1 and figure 2).

Environmentally Friendly

New environmental concerns have greatly reduced the number of "safe" applications for oil/synthetic-base drilling fluids. The PEM system is both non-toxic and non-sheening and can be used safely in areas where other high-performance fluids are excluded. The PEM system allows for safe, easy disposal of mud and cuttings, eliminating clean-up costs.

Because environmental restrictions differ from region to region and year to year, we developed the PEM system as a flexible drilling fluid. Formulated from a number of our specialty drilling fluid products, the system is easily modified to meet a wide variety of regulatory requirements.

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