Successful Application of Well Testing and Electrical Resistance Tomography to Determine Production Contribution of Individual Fracture and Water-Breakthrough Locations of Multifractured Horizontal Well in Changqing Oil Field, China

Abstract

Abstract It is observed that production rates decline quickly and water-cut rises to 90% only after two or three years’ production for many multifractured horizontal wells (MFHWs) in China. Reliable measurements are critical to assess production performance and diagnose water-breakthrough positions to arrange the subsequent operations (e.g. stimulation and water plugging). Although production-logging test (PLT) is an effective method for production performance evaluation, the MFHW might be scrapped during the test and PLT is also expensive for an MFHW. To solve this problem, this paper proposes an approach to determine the production contribution of individual fracture and locate water-breakthrough segments along horizontal wellbore by combination of well testing and electrical resistance tomography (ERT). Firstly, a well testing model is developed to model pressure behavior of an MFHW intercepted by asymmetric fractures with arbitrary locations, unequal conductivity and production. Secondly, model validation demonstrates the accuracy of the well testing model proposed in this paper. Thirdly, sensitivity analysis shows that early-radial flow becomes remarkable as spacing between producing fractures or numbers of producing fractures decrease. N* is defined to characterize the number of mainly producing hydraulic fractures (NMPHF), and the value of N* depends on fracture properties (e.g. half-length, spacing, conductivity) besides the NMPHF. Fourthly, the well testing model is applied to estimate the flow profile through history matching of bottomhole-pressure (BHP) data. Fifthly, the introduction of ERT method solves the difficult to distinguish oil and water profile compared with well testing method, enables us to monitor the water-breakthrough locations and reduces the multiplicity of well testing interpretation in well performance evaluation. Finally, this method has been successfully applied to Changqing Oil Field, and results obtained by well testing and ERT method coincide with PLT, which enable petroleum engineers to carry out stimulation strategies to improve production performance and decrease the water-cut of MFHWs.