Integrated workflow of temperature transient analysis and pressure transient analysis for multistage fractured horizontal wells in tight oil reservoirs

Abstract

Multistage hydraulic fracturing of horizontal wells is one of the most effective techniques for developing unconventional reservoirs. Understanding the amount and location of hydraulic fractures is of great significance for guiding reservoir development. Pressure is by far the most commonly used data for hydraulic fracture analysis. However, for complex hydraulic fractures, pressure inversion procedure inevitably produces multiple solutions, which may lead to errors in production prediction and optimization design. In recent years, the application of distributed temperature sensors makes it possible to real-time monitor the wellbore temperature distribution. By using the integrated inversions of temperature transient analysis (TTA) and pressure transient analysis (PTA), we can eliminate one degree of freedom and address the above problem of multiple solutions. In this study, a thermo-hydraulic coupling mathematical model is proposed to describe the temperature and pressure fields for multistage fractured horizontal wells (MFHWs) during the single-phase oil production process. Then, the above model is numerically solved by using COMSOL Multiphysics. Accordingly, the time-dependent pressure drop and complex nonlinear heat transfer are investigated in detail. The results show that convective heat transfer occurs in the vicinity of the intersections of the hydraulic fractures and the wellbore. This causes the temperature change of the above intersections is quite different from that of other sections of the wellbore. Thereby, the locations of hydraulic fractures can be identified from the temperature time derivative curve. On the other hand, the length of hydraulic fractures can be obtained by conventional PTA. Consequently, the geometries and the conductivities of hydraulic fractures can be determined by integrating workflow of TTA and PTA. This depicts that TTA can serve as a companion means of PTA to investigate the distribution of hydraulic fractures.