The First Integrated Formation Evaluation of Shale Gas in Horizontal Wells Using An Efficient and Economical Logging Method Involving Conveyance Through the Drill String and Bit: A Case Study in Huangjinba Block, China

Abstract The performance of shale gas wells varies, and the heterogeneity of shale gas reservoirs requires a good understanding of both reservoir quality (RQ) and completion quality (CQ) of the formation. There are many choices for data acquisition in shale gas horizontal wells, such as wireline conveyance and logging while drilling (LWD). The operator needs to balance between costs, risks, availability of certain measurements and quality of data acquisition. This paper shows a new logging method using a slim tool string that is designed to be conveyed though the drill string and a hollow bit, and the memory data can be obtained when the tool is tripping out. It shows great advantage in lowering the costs, reducing the risks and saving the rig time, when compared to other logging methods. The quad-combo logging suite incorporates spectral gamma ray, density, compensated neutron, array induction resistivity, and array sonic measurements. An integrated formation evaluation derived from the quad-combo data provides answers to RQ and CQ of the shale gas reservoir, which can be the guide for the hydraulic stimulation. Case studies are presented from shale gas reservoirs of Huangjinba Block in Zhejiang Oilfield of PetroChina, which is located at the Zhaotong area of Northern Yunnan and Guizhou provinces. The environmental corrected quad-combo data from the new slim logging tool proves to be consistent when compared with the wireline data in the pilot hole and LWD data in the offset horizontal wells, using a heterogeneous analysis method. A robust and comprehensive petrophysical description of lithology, porosity, permeability, total organic carbon content (TOC), gas content, fluid saturation, and tri-axial stress magnitudes is presented. A new understanding of shale gas reservoir heterogeneity is established. Engineered completion design based on the RQ and CQ has demonstrable value in improving perforation efficiency and production performance. This paper discusses a novel application of a new slim logging tool in formation evaluation of shale gas horizontal wells, and it proves to be efficient and economical. It makes the engineered design for the hydraulic stimulation possible and a success. The workflow can also be applied to other shale gas plays in China.