Exploration of integrated technology for deep coalbed methane drainage in full life cycle: A case study of Daning‒Jixian Block

The first deep coalbed methane (CBM) field with a depth of more than 2 000 meters in China has been proven in Daning‒Jixian Block on the eastern margin of Ordos Basin, where the deep coal bed has the characteristics of large buried depth, high pressure, high gas content, high gas saturation and low permeability. Besides, the features of early gas occurrence, high gas-liquid ratio and high salinity of produced liquid are shown in the production process. Problems such as corrosion, anti-eccentric wearing, gas locking and pump blocking were encountered in the application of suction pump based lifting system in the trial wells of this block, which resulted in the poor continuity of gas drainage, bringing a series of challenges to the cost reduction and efficiency enhancement in the development of gas field. Through analyzing and summarizing the main factors affecting the continuity of gas drainage, the idea of “three-stage” integrated technology for drainage in full life cycle, with production by self-energy in early stage, plunger lift in immediate stage and gas lift combined with plunger lift in later stage, was innovatively proposed based on the main type of horizontal well developed currently according to the production parameters and the change of gas-liquid ratio in different stages of deep coalbed methane, for the purpose of fundamentally solving the problems existed in the suction pump based lifting system, ensuring the continuous stable production of gas well and reducing the cost of drainage equipment, as well as its operation and maintenance cost. Presently, the drainage technology in the early stage of production has been tested on site, which could satisfy the requirements of continuous stable drainage. Further, the exploration on innovative integrated technology of drainage, with breakthrough made, could be of great significance to the efficient drainage in the large-scale development of deep coalbed methane in the future.