Successful Hydrajet Acid Squeeze and Multifracture Acid Treatments in Horizontal Open Holes Using Dynamic Diversion Process and Downhole Mixing

TLDR

Stimulation of long, open‑hole horizontal completions in low‑permeability carbonate reservoirs is challenging because live acid must be channeled precisely; mis‑direction wastes fluid and makes creating extended fractures or wormholes nearly impossible. The study aims to evaluate and compare conventional acid treatments with hydrajet fracture‑acidizing techniques in several open‑hole horizontal wells within the same formation. Hydrajet fracturing employs dynamic fluid diversion to target specific fracture entry points and high‑pressure downhole mixing of two independent fluid streams to generate foam for intense acid squeezes, producing a homogeneous mixture. Results from multiple wells indicate that hydrajet treatments differ from conventional acid treatments, with the new process achieving more effective fracture initiation and acid placement.

Abstract

Abstract Effective stimulation of wells with long, openhole horizontal completions is generally considered a difficult task, especially in low-permeability carbonate reservoirs that require deep penetration with live acid. Because the creation of multiple effective fractures, the opening (etching) of existing fractures, or the creation of extensive wormholes is generally desired, this task becomes even more difficult, time-consuming, and expensive if conventional acidizing processes are used. If the live acid is not channeled properly, it will be spent rapidly at unwanted locations, often greatly enlarging the fluid-entry point. Under such circumstances, creating etched fractures or wormholes of any significant lengths can be nearly impossible. A relatively new hydrajet fracturing process can be used to solve this problem. This process can be used in two ways: (1) dynamic fluid energy is used to divert flow into a specific fracture entry point to initiate a fracture at the intended location with live acid directed into this fracture plane, (2) high-pressure downhole mixing is used to create foam for high-intensity acid squeezes. This technique typically uses two independent fluid streams, one in the treating string and another in the annulus. The two fluids (if dissimilar) are mixed downhole at a tremendously high energy to form a homogenous mixture. This paper discusses and compares the results of conventional acid treatments with various styles of hydrajet fracture-acidizing treatments performed in several openhole horizontal wells within two different areas of the same formation. The novel use of the downhole mixing feature is also discussed.