Engineering Cementing Solution for Hutubi Underground Gas Storage Project

Abstract

Abstract Underground gas storage 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 underground gas storage with a storage capacity of 4.5 × 109 m3. A total of 37 wells will be drilled with 30 natural gas injection/withdrawal wells, 5 observation wells, and 2 water injection wells. Underground gas storage 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 leakage of the gas and flow through the caprock. A specialized cement technology was identified as a solution to underground gas storage and was deployed successfully in the Hutubi field with great results. The cement selected had to meet the pressure and temperature challenges associated with the underground gas storage, 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.