Wellbore cooling and heat energy utilization method for deep shale gas horizontal well drilling

Abstract

The downhole high-temperature problem has become a bottleneck that restricts the efficient development of deep shale gas resources in China. This study highlights the characteristics of the deep shale gas drilling process to develop a transient model of wellbore temperature distribution for deep shale gas horizontal section drilling through thermal resistance analysis, which is verified using experimental and field data. Based on this model, the influence of the circulation time, drilling fluid flow rate, drill pipe rotation speed, rate of penetration, drilling fluid inlet temperature, and drill pipe thermal conductivity on the wellbore temperature distribution during horizontal well drilling is investigated. The results indicate that an insulated drill pipe is the most effective measure for cooling down the wellbore. Subsequently, a system for wellbore cooling and heat energy utilization while drilling based on insulated drill pipes is established in conjunction with the organic Rankine cycle. The results show that the estimated maximum power generation of this system was 990.120 kW when the bore diameter is 215.9 mm, the design depth of the well is 6095 m, the vertical depth of the well is 4313.76 m, and the inlet temperature is 20 °C.