First Successful Hydraulic Fracturing in the Offshore Abu Dhabi: Part1—Flexible Design to Unlock a Tight Gas with Uncertainties—

Abstract

Abstract The hydraulic fracturing technology is widely applied in tight reservoirs, including shale reservoirs, as one of the established reservoir stimulation methodologies to enhance the productivity. Even though the hydraulic fracturing is currently a common technique, there are remaining challenges in offshore fields with the high degree of geological and geomechanical uncertainties. In offshore hydraulic fracturing operations, key issues are the limited deck space for the required equipment on-board and economical aspects of the surface equipment including stimulation vessels due to the limited number of dedicated offshore stimulation vessels in the world. In addition, the limited reservoir information brings uncertainties in the hydraulic fracture design and causes difficulties in finalizing the operation plans from the timing and logistics point of view. This paper contains the first part of the two successive parts of a case study will be shown on successful optimization and productivity enhancement of actual offshore hydraulic fracturing for a deep tight gas reservoir with considerably limited formation data and under a high-pressure and high-temperature (HP/HT) environment. This successful operation was recognized as a landmark in this region, in terms of the first hydraulic fracturing operation in the offshore Abu Dhabi. In this paper (part 1), we describe how the flexible hydraulic fracture design led to an efficient productivity enhancement. The hydraulic fracture design was optimized by the integrated data acquisition strategy and the successive flexible adjustment from the design stage at office to the actual main treatment at wellsite. The relevant fracture design components like proppant usage and size can be optimized, based on sensitivity studies assuming not only all possible geological and geomechanical circumstances but also the actual pre-frac well test and data-frac results. In part 2, the key factors will be highlighted on this successful hydraulic fracturing result against the difficulties from operational point of view (Al Ameri et al. 2014). The work flow and successful strategy in our hydraulic fracturing design and execution can be applied to other offshore tight-sand gas reservoirs including those under HP/HT condition. The optimized design of hydraulic fracturing provides an effective operation and enables more economical field development for the tight reservoirs.