Production Logging of Shale Gas Well in China

Abstract China is the first country achieving shale gas breakthrough outside the North America. Fuling shale gas play is one of the most successful shale gas reservoirs by far in China. However, production loggings of shale gas wells illustrate that only about one third to one half of hydraulic fractures produces. Meanwhile, the productive fractures contribute differently to the production rate. Therefore, production logging technology is needed to evaluate the production status and contribution per stage or cluster, and get clear understanding of post-fracturing performance. The paper generalized the difficulties and challenges for production logging taking the geology and well condition into consideration in Fuling shale gas play in China. These challenges include snubbing operation, production logging tools selection, tools conveying, unclean wellbore and complex flow regime in horizontal wellbore. Aiming at solving the above the difficulties, one design of coiled tubing conveyed combination of conventional tools with single sensor and array tools with multiple sensors is formed. The array tools are used to diagnose fluid phase and measure gas/liquid holdup, thus data from single sensor tools and multiple-sensor array tools measurements can be combined to enhance the quality of the interpretation results. By comparison, the coiled tubing is more suitable for conveying the downhole tools in deep well with long horizontal wells. The Appropriate coiled tubing diameter is chosen and the coiled tubing passing ability in the horizontal lateral is simulated. The characteristics of array testing tools produced by Schlumberger and Sondex are analyzed. Since the array tools have the potential risks of being blocked or even damaged by fragments of bridge plugs, therefore, the borehole cleaning technique is considered. By statistics of wellhead pressure of shale gas wells in Fuling shale play, the BOP should be with pressure capacity over 50 MPa. One case well in Fuling shale gas play shows that it is feasible to use coiled tubing conveyed array tools for production logging in shale gas well. The testing data interpretation results demonstrate the reliability of data interpretation method and the significance of production logging. For the case well, one half (6 stages out of 11 stages) fractures produce gas and the other half contribute nothing. The productive fractures also present different performance and the most predominant fracture contribute 36.47% of the total production. By production logging, not only fracture contribution to total production rate can be obtained, the flow regime and dynamic liquid level can also be determined. The production logging can be helpful for downhole fluid dynamic analysis and production optimization, and it may partly help the design of horizontal laterals and fractures scenarios.