Abstract
In the past five years, as one of the most active country for the shale gas development all over the world, China has been experiencing a boom of shale gas development. In 2017, the total yearly production of shale gas has reached about 350 BCF in China. As the planning goes on, the yearly production will reach 1000 BCF in 2020. The market is huge regardless that the task is difficult.
There are four national shale gas demonstration plots in China, CW plot, JSB plot, ZT plot and YA plot. JSB plot is the first to obtain breakthrough for the shale gas development, contributing the half of the total yearly production of shale gas in China. CW plot is the second successful plot, which contributes about 30%. This paper will describe the casing deformation which is the knottiest problem not only CW plot but for all plots.
The casing deformation of shale gas wells in China happens frequently, which restricts the gas production to a great extent. This paper describes the application of temporary-blocking fracturing technology in a casing-deformed shale gas well to minimize the loss. In this well, only one stage of hydraulic fracturing is conducted leaving 19 stages (about 1400m) untreated due to the casing deformation. First of all, the wiper trips are made to confirm the deformation point is around the drilling target spot A, and the maximum drift diameter decreases from 114mm to 83mm. Since there is no smaller bridge plug, then the temporary-blocking fracturing techonology is determined to be conducted. 16 stages are designed for the 1400m interval. For feasibility, the 16 stages are separated into 8 rounds of fracturing. A total of 7756 blocking balls and 2750kg blocking agent are used to block the perforations for the 16 stages. To enlarge the stimulated reservoir volume (SRV), the volume of fracturing fluid and the quality of proppant injected for one stage are designed as 53Mcf and 120t respectively. The treatment pressure indicates that the pumped blocking agent is effective. From putting the well on production, the average daily production is 3.53MMcfd which is no less than that of wells without casing deformation in the same pad. Based on the chemical analysis of the collected flowback fluids, the blocking agent is 100% dissolved and has no damage to the formation. The application of this technology successfully solves the problem of casing deformation so as to reduce the production and economic loss.
