Overcoming OBM Filter Cake Damage Using Micro-Emulsion Remediation Technology across a High-Temperature Formation

Addagalla, Ajay Kumar V. (Baker Hughes) | Kosandar, Balraj A. (Baker Hughes) | Lawal, Ishaq G. (Baker Hughes) | Jadhav, Prakash B. (Baker Hughes) | Imran, Aqeel (Baker Hughes) | Al Saqer, Qassem R (Baker Hughes) | Sherbeny, Wael El (Baker Hughes) | Ansari, Adel (Saudi Aramco) | Pino, Rafael (Saudi Aramco) | Gad-Alla, Ahmed E (Saudi Aramco) | Olivaresantunez, Tulio (Saudi Aramco)

OnePetro 

Abstract

Formation damage is one of the main concerns at various stages of drilling, completion and production processes and is attributed to many factors. Either in open-hole or cased-hole completed wells, hydrocarbon flow in the reservoir may be impeded by various damaging mechanisms such as in-situ emulsions, water block, organic deposition and oily debris left downhole.

Micro-emulsion fluids are thermodynamically stable, optically transparent solutions of two immiscible fluids formulated with a specialized surfactant blend and/or co-surfactant. They differ from normal emulsions because they can be prepared with little or no mechanical energy input. They typically comprise a non polar (oil) phase, a polar (aqueous) phase, surfactant(s) and an optional co-surfactant. Depending on how they are formulated, mesophase fluids can exist in a single-phase or in a three-phase system wherein the middle-phase microemulsion is in equilibrium with excess water and/or oil.

The formulation characteristics, phase type, and ultimately, the cleaning efficiency of a microemulsion are dictated by the hydrophilic-lipophilic balance between the surfactant(s) and the physico-chemical environment. The microemulsions described in this study are single-phase where oil and water are co-solubilized by the surfactant(s) and co-surfactants. The water/oil interface has a zero or near-zero curvature, indicative of the bicontinuous phase geometry that produces very low interfacial tension and the rapid solubilization of oil upon contact. The formation of a micro-emulsion alone does not ensure the fluid will solubilize oil effectively to leave surfaces water-wet. The micro-emulsion behavior and cleaning efficiency can be influenced by salinity, surfactant, co-surfactant, oil type, temperature and particulates. No two wells are identical and the physical and chemical conditions can vary greatly depending on the application. As a consequence, robust, optimized formulations are necessary and validation testing is required to determine the efficacy of a mesophase for a specific application, i.e., OBM displacement/cleanup and removal of formation damage in openhole and cased-hole wells.

Micro-emulsion fluids were successfully developed to effectively resolve the persistent problem of near-wellbore damage. The physico-chemical properties of the micro-emulsion systems include high oil solubilization, high diffusion coefficients through porous media and the reduction of interfacial tension between organic and aqueous phases to near-zero, making them excellent candidates for removing formation damage. The chemistry of micro-emulsion fluids makes the systems excellent choices for superior synthetic or oil-based mud (S/OBM) displacements in casing and for OBM filtercake cleanup in openhole completion applications.

This paper presents a technical overview of micro-emulsion technology and field application in a high- temperature gas environment that demonstrate its efficiency in removing Non-Aqeuous Fluid (NAF) debris and filter cakes, whilst reducing near-wellbore damage and improving well productivity and solids mobility.