Key technologies for the open hole completion testing of ultrahigh temperature and high pressure gas wells in the South China Sea

There is immense potential of oil and gas resources in the ultrahigh temperature and high pressure block of the Yingqiong Basin, the South China Sea. And with the gradual increase of exploration intensity in the ultrahigh temperature and high pressure block, the demand on the open hole completion testing of offshore ultrahigh temperature and high pressure gas well increases gradually. At present, the open hole completion testing of offshore ultrahigh temperature and high pressure gas well is faced with huge risks and challenges as follows. High-density testing fluid can be hardly blown out, which can easily result in the thickening settlement of the testing fluid in the extreme conditions so as to block the testing string. Under the testing conditions of ultrahigh temperature and high pressure, the configuration of testing string is relatively complicated while the string elongation is not designed reasonably, which brings about failure risk to testing tools. The sidewall rocks are of higher instability risk, and there are the risks of hole collapse, sand production and packer burying and sticking. In order to solve these difficulties, this paper developed independently a set of key technologies suitable for the open hole completion testing of ultrahigh temperature and high pressure gas well of offshore efficient exploration and development. The testing fluid of stable settlement type is developed, whose settlement stability is strengthened by adding high-temperature fluid loss agent and increasing lime content on the basis of the original drilling and completion fluid. The structure of the testing string is optimally designed by adding RD circulation valve and selective testing valve on the basis of the conventional testing string and calculating the elongation of the testing string reasonably. The testing pipeline flow and device layout of offshore platform are optimized reasonably, so that the risks in the testing process are reduced effectively. Reasonable testing pressure difference and testing time are set under the premise that no shear damage happens on the sidewall during the testing. These technologies have been successfully applied in Well DF13-Y-Y, an ultrahigh temperature and high pressure gas well in the South China Sea. The successful application of these technologies accumulates valuable experience for the following open hole completion testing of offshore ultrahigh temperature and high pressure wells.