Hydraulic fracturing (HF) has always been the sustainable way to produce a complex HPHT tight reservoir. However, for a reservoir in strike-slip stress regime having millidarcy permeability, temperature of 350 °F and reservoir pressure of 9,500 psi, innovation is imperative for successful exploitation of the reservoir. This paper describes the development of a smart perforate-stimulate-perforate strategy adopted to successfully execute multistage hydraulic fracturing for optimal reservoir coverage and well productivity in a complex HPHT setting.
Borehole acoustic profiling data was used to calibrate and build a robust mechanical earth model (MEM). Based on the calibrated stress profile as proxy for Completion Quality (CQ), intervals requiring HF were determined across lithofacies with best reservoir quality (RQ). Optimal perforation clusters and HF stages were finalized through pre-frac simulations to maximize stimulated intervals and minimize stress shadow interference. Continuous validation and improvement of pre-frac models were performed using data from diagnostic injections and completed stages to generate a post-frac model. Based on the final post-frac model and commingled flow well test results, additional perforations between HF stages were added to increase area of flow.
The tectonic strain–calibrated geomechanical modelling helped in establishing and understanding the in-situ stress barriers in the formation. Pre-job frac models of each stage were seen to be in good agreement with diagnostic injection tests and temperature logs. Injections test results helped in deciding the optimal pumping schedule and dynamic parameters of the stimulation treatment. Post-fracturing pressure matching was used to determine the stimulated geometry and revise the subsequent perforation interval and stimulation design. A payzone of more than 200 m—initially planned for three HF stages as per historical experience—was successfully completed in four stages with each frac placing more than 300,000 lbs of proppant. Optimal coverage of the entire payzone resulted in a 50% increase of production in comparison with previously completed wells in the field. Production logging data during post stimulation flowback revealed zonal contribution and an abnormally high differential between flowing pressure and reservoir pressure. Add-on post-stimulation perforations helped in mitigating this problem, resulting in an additional 20% increase in well productivity.
Complicated stress regimes and paucity of core data have often made HF treatment optimization very challenging. This paper covers the integration of representative in situ far-field data from an advanced acoustic tool, supported by pre-frac diagnostic injection tests and post-frac production logs. This data-driven workflow was used to develop a unique perforate-stimulate-perforate strategy to successfully optimize stimulation treatment coverage of the reservoir and maximize well productivity.