Paradigm Shift in Completion Limits: Open Hole Gravel Pack in Highly Depleted Reservoirs Drilled with Well Bore Strengthening Technology

Abstract

Open Hole Gravel Pack (OHGP) completions have been the primary completion type for production wells in the Azeri-Chirag-Gunashli (ACG) field in Azerbaijan for 20 years. In recent years, it has been required to use well bore strengthening mud systems to allow drilling the more depleted parts of the field. This paper describes the major engineering effort that was undertaken to develop systems and techniques that would allow the successful installation of OHGP completions in this environment. OHGP completions have evolved over the last 3 decades, significantly increasing the window of suitable installation environments such that if a well could be drilled it could, in most cases, be completed as an OHGP if desired. Drilling fluids technology has also advanced to allow the drilling of highly depleted reservoirs with the development of well bore strengthening mud systems which use oversized solids in the mud system to prevent fracture propagation. This paper describes laboratory testing and development of well construction procedures to allow OHGPs to be successfully installed in wells drilled with well bore strengthening mud systems. Laboratory testing results showed that low levels of formation damage could be achieved in OHGPs using well bore strengthening mud systems that are comparable to those drilled with conventional mud systems. These drilling fluid formulations along with the rigorous mud conditioning and well clean-up practices that were developed were first implemented in mid-2019 and have now been used in 6 OHGP wells. All 6 wells showed that suitable levels of drilling mud cleanliness could be achieved with limited additional time added to the well construction process and operations and all of them have robust sand control reliability and technical limit skins. Historically it was thought that productive, reliable OHGP completions could not be delivered when using well bore strengthening mud systems due to the inability to effectively produce back filter cakes with large solids through the gravel pack and the ability to condition the mud system to allow sand screen deployment without plugging occurring. The engineering work and field results presented demonstrate that these hurdles can be overcome through appropriate fluid designs and well construction practices.