Oriented Perforations - A Rock Mechanics View

Abstract

Hydraulic fracture initiation dictates the communication path between the wellbore and fracture plane. Nonplanar fracture geometries such as multiple, T-Shaped, and reoriented fractures are not advantageous and they adversely affect the potential to achieve a desired stimulation treatment. Oriented perforation can be the solution to initiate a single wide fracture in vertical and deviated wells. Also oriented perforations may be used to create stable tunnels in poorly consolidated formations thus avoiding sand failure and consequently preventing sand production. This paper presents laboratory experimental results related to oriented perforations for hydraulic fracturing. It also discusses the use of oriented perforation for sand control. Experiments were designed to investigate the effect of perforation orientation in vertical and horizontal wells on hydraulic fracturing treatment. Introduction Oriented perforation has not been widely applied in the industry due to practical difficulties involved in this process. However, more applications are becoming candidates for oriented perforation, i.e., fracturing deviated and horizontal wells, controlling sand production, and solving wellbore instability problems. The first work on the effect of perforation on hydraulic fracturing was presented by Daneshy who showed that the direction of induced hydraulic fracture is not dictated by perforation orientation. He showed that in many cases, fluid traveled from the perforation through the area between the casing and formation to initiate a fracture in the direction of maximum horizontal stress. Several authors showed that the perforation orientation in horizontal wells should be in phase with the anticipated fracture direction. Field observations on the effect of oriented perforation were reported for vertical and deviated wells. Venditto, et al. reported a field observation on a vertical well. P. 411^

Link-up of mini-fractures from perforated holes

“…The rough fracture opening surface and the failure of a mini-fracture linkup from deviated wellbores were reported by Hallam and Last [6], Veeken et al [7], Weijers and de Pater [8]. The propagation of a hydraulic fracture from oriented perforation was also studied experimentally by El Rabaa [9] and Abass et al [10,11]. The experimental observation is in general consistent with the analytical results presented in this section.…”

“…Equation (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) can then be rearranged in terms of the dislocation density parameter A n as follows:…”

Near Wellbore Hydraulic Fracture Propagation from Perforations in Tight Rocks: The Roles of Fracturing Fluid Viscosity and Injection Rate

“…The quality of a hydraulic fracturing operation could be negatively impacted by these issues, and consequently, the fracturing treatment may not improve the production of the wellbore effectively. Such kind of challenges are mainly due to the existence of the perforations cavities which complicate the fracture initiation and near wellbore propagation [5,6].…”

“…Additionally, several experimental studies have been carried out in order to physically model and analyze the mechanism of fracture creation in perforated boreholes [5,6,14]. However they did not scaled down the real field fracturing processes to experimental test samples.…”

Experimental studies

“…The tortuosity on the fracture surface and the failure of fractures to link up from the perforated holes were reported by these authors. The turning of the hydraulic fracture from horizontal and deviated wellbores has been investigated by El Rabaa [15] and Abass et al [16,17] using a tri-axially loaded rock specimen. The turning of the fracture plane toward the direction normal to minimum in situ stress and the excessive friction pressure caused by tortuous fracture surface and roughness at the fracture opening have been observed and reported by these authors.…”