Productivity Optimization and Validation of Multistage Fracturing in a Rare Geomechanical Setting with Production Logging

Abstract

A reservoir with a rare geomechanical setting of higher stresses at shallower depths and vice versa was fractured. The multistage fracture responses were validated using production logging data. Further, production optimization was achieved by understanding the flow profile and geomechanical setting to decide on an optimal flow condition for the wells. An innovative solution-driven approach was identified with production logging playing a key role. Based on the geomechanical model, calculated fracture gradient indicated higher stress in the shallower section and lower stress in deeper intervals. Multistage fracturing was performed. Post fracturing, production logging was carried out in Well A at two different chokes to understand flow behavior in wellbore and correlate with reservoir response. Based on these results, an intermediate choke was selected for production logging in Well B to observe any improvement in flow behavior. An integrated study of geomechanics, fracture performance and production logging resulted in deciding an optimal flow condition for the wells. Results are presented for a two well operation. Production logging results indicated that deeper intervals were producing higher compared to shallower layers, thereby validating the geomechanical model. Also, fissures were encountered during deep stage fractures, indicating potentially high production from reservoir from these stages due to better flow conduit. This was also confirmed from the production logging results. In Well N1, production logging data, in the lower choke, indicated sluggish and unstable flow behavior with the top three stages underperforming. However, at higher choke, a steady and uniform flow was observed. The production logging results were also observed to be in line with the obtained frac-operation parameters on the higher choke. However, an anomaly was observed in the second stage of Well N1, which is estimated to be as a result of fractures closing down due to higher stresses in shallower depths. Based on this, an intermediate choke was selected to flow Well N2 and record production log data to observe and evaluate the flow behavior at a different choke. The flow was still observed to be sluggish and unstable at the intermediate choke. Hence, a final decision was taken based on all the different conclusions to flow the wells at higher choke to maintain optimal frac stage performance and a uniform and steady flow. Rare geomechanical setting of reservoirs presented challenges in accurately characterizing them. The paper recognizes the versatility of the production logging tool in delivering and understanding both reservoir response and wellbore flow conditions. The integration of fracture response with production logging results enabled validation of the reservoir response and provided valuable insights into understanding the flow behavior inside the well, and finally optimizing well productivity.