Coiled-tubing integrated fracturing technology of multiwell cluster in Sulige tight gasfield

In recent years, the multiwell cluster development mode of large well group with multiple well types is the main development mode of tight sandstone gas reservoirs in Sulige Gas Field. However, the mechanical separate layer fracturing technology cannot satisfy the technical development requirements of multilayer high displacement fracturing. For this regard, high-displacement mixed water fracturing technology suitable for tight gas fields was designed according to the theory of volumetric fracturing and the injection mode of slick water+base fluid+crosslinked fluid with low viscous fluid ratio of 40%−75% and displacement of 6−8 m³/min was adopted. Then, to satisfy the requirements of continuous unsetting and setting, the coiled tubing and undersealing differential pressure tool string was developed i.e., guide centralizer & mechanical collar locator & mechanical anchor & Y211 packer & balance valve & ejector & mechanical safety release sub & slip type connector outside the coiled tubing & coiled tubing. In order to ensure the construction safety, the wellhead protector of coiled tubing was developed. Based on the whole-process sand control technology, the standard flow of ground operation was formulated. Thus, the support technologies for safe operation were developed. In addition, the flowback fracturing fluid treatment device was developed, so that the recycle of flowback fracturing fluid was realized. In this way, the coiled-tubing integrated fracturing technology of multiwell cluster is ultimately formed in Sulige tight gas field. By December 2018, this technology had been tested on site in 201 wells of 32 well groups. It is shown that the post-fracturing production rate per well is 15% higher than the reference well and the average fracturing cycle per well is shortened to 11.0 d from 19.5 d (conventional model). It is indicated that this technology is remarkable in production and ROP improvement.