Solving the Low Injectivity Challenges in Hydraulic Fracturing Tight Gas Reservoirs - Case Histories Review
Alexey Yudin, Nurlan Nurlybayev, Ziad Al-Jalal
Abstract
Abstract Fracturing in tight and deep gas formations can be challenging when near-wellbore stresses reduce injectivity. The drilling fluid may contribute to a near-wellbore damage, and this will exaggerate the rock breakdown limits additional to the high local stresses. The paper will present case history review of different techniques in addressing low injectivity in tight gas wells to minimize delays in operations and associated risks. Different stimulation techniques are utilized to enhance the production from tight gas carbonates reservoirs, including multistage fracturing completions and techniques as plug and perf, sliding sleeve systems, coiled tubing conveyed stimulation systems, etc. regardless of completion method type, the damage level could still be present, in addition to the stress cage around the wellbore, hence the injectivity can be very challenging. There are frequent cases, when during the injection stage the pumping rate barely reaches 1 bpm at maximum allowed pressures. And there are several solutions, such as acid squeeze treatment conveyed by coiled tubing, abrasive jet perforations, bullhead acid spearhead stage at lowest pumping rate, completion fluid solvents and others. Each method has different criteria for applicability, depending on the technical scenarios and require critical decision-making process during the operational performance. Due to damage presence in the near-wellbore zone, the injection rate was observed to be below 1 bpm and surface pressure could be reaching the completion limitations, and the possibility of job cancellation becomes high. Therefore, proper solutions were required to improve the injection prior to fracturing treatment. The case study showcases some statistical analyses of solving the challenges concerning the near-wellbore damage and improving the injectivity prior to main stimulation treatment. The case studies review will help optimizing the technical decision when injectivity challenges occur in tight gas reservoirs and could be used as a reference in other HPHT fracturing projects.