Engineering Cementing Solution for Hutubi Underground-Gas-Storage Project

Abstract

Summary Underground gas storage (UGS) is an important segment in China's gas market. Because of the supply-and-demand misbalance of natural gas, the gas in underground storage is made available during the peak winter season. In the west of China, the Hutubi dry-gas field is to be used for UGS with a storage capacity of 4.5 × 109 m3. A total of 37 wells will be drilled with 30 natural-gas-injection/-withdrawal wells, five observation wells, and two water-injection wells. UGS relies on proper wellbore construction and the sealing function of the caprock. The selection of the type of cement is crucial to having a healthy well that will last to meet the gas-storage need of 30 years under high-intensity injection. The gas injection and withdrawal will induce different stresses on the cement sheath and may destroy the seal by either debonding (microannulus) or cracking; an effective cement system is required to prevent the leakage of the gas and flow through the caprock. A specialized cement technology was identified as a solution to UGS and was deployed successfully in the Hutubi field with good results. The cement selected had to meet the pressure and temperature challenges associated with UGS, and a methodology was established to qualify the new sealant. Case histories of three wells illustrate the steps taken in cementing UGS wells in the field.