(54c) Development of an Environmental Friendly Pseudo-Oil Based Fluid for Shale Stability

Shale instability is one of the major concerns for unconventional exploration and production. Conventional water-based fluid (WBM) system performs poorly in shale formations and causes serious shale stability problems. Oil-based fluid are commonly used in shale drilling, which have serious environmental issues and huge cost compared to WBM. Development of a Pseudo-Oil Based Fluid, which is water based but has the properties to stabilize shale formation as OBM, is attractive to shale drilling from both environmental and economic perspectives.

The main source of shale instability is the change of stress state and shale strength through shale-fluid interaction. The components of shale include water sensitive materials, which increases volumes when exposed to aqueous environments. With conventional water-base drilling fluids, shale formations may swell and slough as a result of interaction with the drilling fluid. Furthermore, the shale disperses into colloidal sized particles of clay has an adverse effect on drilling fluids. Inhibiting shale-water interaction during drilling can increase the wellbore stability.

In this paper, a Pseudo-Oil Based Fluid is developed by using a Cationic alkyl ployglycoside (CAPG) surfactant, which is from natural agricultural products, aliphatic alcohols, and amine reagents. The CAPG is particularly effective as a shale inhibitor, it creates a protection coating at the surface of the shale and isolates the shale. Thus, the water-shale interaction is significantly inhabited. Since CAPG is synthesized by using natural products, and it is completely environmental harmless and can decompose quickly after the drilling completed.

The pseudo-oil based drilling fluid is tested under field conditions and compared to the original oil-based fluid. A system including K-PAM as viscosifier, JA-B as Polyamines inhibitor and CN as temperature resistance agent is developed to be used with CAPG to get the desired fluid properties. Results show that the two fluids have almost the same rheology and lubricity, and slightly lower inhibitive ability. This work provides an environmental friendly and economic approach to stabilize shale formations.