Development and field application of combined sliding sleeve staged fracturing string

In order to realize high-efficiency stimulation and production of high-displacement unrestricted volume fracturing and complex interval production control, a combined staged fracturing technology was developed to set the ball-actuated sliding sleeve at lower stable intervals and the switch sliding sleeve at upper production control intervals. First, the balls are dropped to open ball-actuated sliding sleeves successively and the corresponding intervals are fractured. Then, the separating spheres are thrown to isolate the intervals that have been fractured in the lower part. Finally, switch tools of coiled tubing are run in hole to conduct specific fracturing by switching on or off each switch sliding sleeve selectively according to the formation conditions. If any problem occurs in the interval with switch sliding sleeve in the process of later exploitation, another switch string of coiled tubing should be run in hole to isolate the interval in problem while the other intervals are kept in normal production. This combined sliding sleeve staged fracturing technology was applied in Well Su 75-60-34H with three switch sliding sleeve intervals and seven ball-actuated sliding sleeve intervals. The fracturing effect is better than the expectation with displacement rate of 9.2 m3/min, fracturing pressure of 72 MPa and daily gas production 20×104 m3. It provides the technical reference for the one-to-one fracturing and production control of each interval in complex oil and gas reservoirs.