The Technology of Multi-Stage Acid Fracturing in Horizontal Well for Carbonate Reservoir by Temporary Plugging Ways in the Tahe Oilfield

During the course of multi-stage acid fracturing in open hole of horizontal wells in the Tahe Oilfield, "packer+slide sleeve" methods are featured with high operation costs, long working cycle, complicated stage fracturing, low reliability of relevant tools, difficult to handle the tools left in the hole etc. To eliminate these problems, "fiber+particles" composite temporary plugging operations have be used to replace the conventional "packer+slide sleeve" techniques. Upon completion of acid fracturing in a single interval, "fiber+particles" can be injected to generate barriers at opening of fracture, the crack initiation will be in the next section, hereby the sectional fracturing can be performed without staged tools. Through laboratory tests, the temporary plugging fibers with temperature resistance up to 120℃ have been deployed, its dissolution rate is below 40% in fresh water and hydrochloride acid under temperature of 120℃ for two hours, which keeps satisfactory temporary plugging effect and has ultimate dissolution rate of 100%, no damage to reservoir formations. Mass fractions of fibers and particle size were optimized, i.e. fiber length of 6-8 mm with mass fraction of 1.0%-2.0%, particle size of 1.0 mm with mass fraction of 0.5%, temporary plugging pressures 9 MPa. The techniques have been applied for 8 times in the Tahe Oilfield, with initial plugging pressures of 6.6-9.0 MPa, the single well production capacity has been raised significantly, and operation cost lowered, cumulative increase of oil 5.6×104 t. Research results showed that temporary plugging and staged acid fracturing for horizontal wells did not require the staged tools, so it can eliminate the problem of running and pulling relevant tools that ever used in conventional operation in horizontal wells of carbonate formations in the Tahe Oilfield.