In a case study of four wells located in offshore Sabah Malaysia, a field application using microemulsion technology to develop a customized in-situ breaker solution enhanced production rate by removing oil-based mud (OBM) and synthetic based mud (SBM) filter cake and remediating near-wellbore damage. All wells were completed as open–hole horizontal wells. Key challenges of the field are the multiple sand layers interbedded with intra-reservoir shale intervals necessitating a complex well trajectory and an operational preference for drilling with SBM drill-in fluid (SBM DIF). Lower than expected production rates were associated a water-impermeable SBM DIF filter cake and solids residue resulting from a conventional breaker system being unable to fully remove emulsion damage and effectively disrupt the filtercake.
A series of laboratory tests for return permeability using formation cores from the offset wells and ceramic discs were completed as part of a feasibility study prior to field trials of the new microemulsion breaker system - a customized formulation consisting of a proprietary surfactant blend, organic acid, corrosion inhibitor and brine designed to remove the damage caused by the SBM DIF and restore open-hole flow conditions. The new breaker system has ultra-low interfacial tension which, when pumped into the open-hole section and allowed to soak for a sufficient period of time, diffuses into the rock matrix and forms an in-situ microemulsion completely and uniformly cleaning the near wellbore environment of SBM DIF residue, dispersing solids and leaving all surfaces water-wet.
Laboratory results described in this paper show that the customized microemulsion breaker has the capability to remove SBM DIF filter cake, remediate emulsion damage caused by SBM-DIF, and restores the rock matrix back to its original permeability and predrilled state. All four wells in this field application have exceeded their expected production rate. The customized microemulsion breaker is the major contributing factor.