An Innovative Rheology Modifier Which Provides Dual Function : Achieves Non-Damaging Clay Free System for Reservoir Drilling and Flat Rheology for Deep Water Drilling

Exploration and Production operators prefer non-damaging non-aqueous fluid (NAF) for drill-in reservoirs. One of the requirements of non-damaging system is clay free system and it should perform as good as any conventional NAF. For deep water drilling, it is necessary to have flat rheology of NAF over a wide range of temperatures. An innovative rheology modifier which provides clay free system and also offers flat rheology profile has been developed and successfully used in field. The rheology modifier can minimize or totally eliminate the need of organophilic clay to improve the quality of non-damaging reservoir drilling fluid. The paper will discuss the chemistry of newly developed polyamide resin-based rheology modifier and compare it with other poly-amide resin chemistry currently used in industry. Also, the critical parameters which are required to synthesize cross-linked polyamide resin that provide thixotropic properties to NAF will also be discussed The newly developed clay free system utilizes a single rheology modifier component to provide dual functions of providing true clay free system and offers flat rheological profile over wide range of temperatures. The dual function is achieved without sacrificing the vital mud parameters, such as emulsion stability, fluid loss control and rheology. In fact, these mud parameters are enhanced due to surfactant characteristic incorporated in newly developed poly-amide resin-based rheology modifier. The clay free system can be formulated for deep-water applications with mud weights up to 18.0 lb/gal and temperatures up to 350°F. Recent successful field trials as a clay free system for drilling reservoir indicated that the new system is easy to maintain and provides good fluid performance in terms of drilling rate, ECD management, and hole cleaning. This product provides an excellent rheological profile at a low dosage of 1 ppb. Even at this low dosage, LSRV was above 10 in 8 ½" Hole with yield point of greater than 15 lbs/100 ft2. When the system was contaminated with a severe saltwater flow, there were no fluid-related problems before the synthetic oil/water ratio was restored.