Well Performance Analysis in Shale/Tight Gas Reservoirs: Case Study Review

In recent years, the shale and tight reservoirs have emerged as one of the top resource plays for securing the world energy demand. Because of extremely low permeability nature of tight reservoirs, the advanced drilling and completion techniques are required to adjust economic production from these reservoirs. The current industrial practice is to drill long horizontal wells with multi-stage hydraulic fractures. The goal of multi-fractured horizontal well is to create a larger contacted area between the well and tight rock and in turn, make it easier for the fluid to flow toward the producing well. However, as development proceeds, the analysis of the data and accurate forecasting of the well performance is still facing challenges. In fact, as more data become available, it is becoming more clear that the conventional reservoir engineering may no longer be accurately valid to analyse the production data of shale reservoirs. As a traditional evaluation process, the early-time production rate (IP) is used as a proxy for ranking the well performance and estimating the ultimate recovery (EUR) and, therefore, forecasting the economic viability of individual wells. However, as it is shown in this paper that the IP analyse is not the most accurate measurement and sometimes can be indeed a misleading parameter in shale/tight wells evaluation. Alternatively, more advanced reservoir engineering tools and parameters are required to interpret the performance of the well and forecast the production of shale reservoirs. This study uses production data analysis to estimate the productivity trend of shale wells in the reservoir of interest. Our dataset is limited to a restricted geographic area with presumably consistent geological properties such as porosity, water saturation, pressure, and temperature. With limited variation in reservoir properties, the flow trend of the well becomes a good metric for completion efficiency. The production data from a few typical shale gas wells are provided and the well performance is evaluated using rate transient analysis tools. The long-term production forecast of the wells is then estimated using empirical models. The results of this study would help operators/investors to better understand the challenges they may face with as well as possible opportunities in shale reservoirs. This study would also help operators to decide about the best completion approach to achieve optimal production within a shale region.