Research And Application Of Gas Storage Well Cementing Quality Testing And Evaluation Techniques

As clean and environmentally friendly high-quality energy, natural gas has many advantages such as high conversion efficiency, low environmental cost, less investment and short construction period etc. Positive development of natural gas resources has become the whole world energy industry trend. The natural gas has been highly regarded in city gas source selection in china. Along with the wide application of natural gas, the number of CNG station is increasing. High pressure underground gas storage well (herein after referred to as the gas storage well) as a new storage device to store compressed natural gas in CNG station, is a tubular, vertical pressure vessel underground, with less occupied area, strong security, low operation costs, simple and convenient operation and maintenance etc.Gas storage well will be constructed underground (the maximum depth of300m) and supported with concrete. The electrochemical corrosion in Stratum and fatigue can cause local wall thinning; there exists great potential safety hazard. The good cementing quality of Gas storage well manufacturing process means that the cement sheath surrounding outside wellbore can separate the wellbore buried in the ground from external corrosion environment, As well as the concrete support can also sustain the whole Gas storage well and keeps the natural gas from leakage and spreading above the ground. Therefore the cementing quality is very critical during the construction process. According to the gas storage well accident and expert opinion, General Administration of Quality Supervision, Inspection and Quarantine of the Peoples of China requires that the cement surrounding the new manufacturing gas well should cocoon the whole well. So that we can evaluate cementing quality of manufacturing process and to ensure the safe operation of gas storage well bade on the gas well cementing quality detection and evaluation.Several type of systems have been developed for the evaluation of the oil&gas storage well cementing quality, such as the CBL, varying density logging(VDL), and ultrasonic pulse echo logging, and sector area concrete bonding evaluation instrument. Currently in China CBL and VDL are mostly utilized for the evaluation of the concrete support for storage wells.To meet the practical needs of the development of Gas storage wells in Shandong Province and the requirements in national regulations, this paper deeply investigated the design, constructions, and inspections of the underground Gas storage wells, and specially studied the supporting technologies for Gas storage wells, based on which we conducted technical research on quality evaluations on Gas storage well concrete support. Based on methodologies for evaluation of the Oil&gas well concrete support and special features of the Gas storage well, we developed an instrument aimed for the inspections of the Gas storage well concrete support. This developed instrument includes two parts, the Gas storage well concrete bonding inspection equipment (with the cooperation of Xian Da Bo Petroleum Technology Co., Ltd.) and the quality evaluation software (With the cooperation of the Beijing Shida petrosoft Technology Co., Ltd.). Based on our tests over more than370Gas storage wells, we studied the influence of the construction techniques, cement properties on concrete support qualities.Gas storage well manufacturing is a special process, once cementing quality is poor, it is difficult to repair. Two reinforcements are proposed based on analysis and calculation of storage wells cementing quality unqualified failure mode.