Challenging Traditional Practices in Conventional Reservoirs: Overflushing, Water Conformance and Pillar Fracturing Combination, S Field, Ecuador

Abstract

We discuss the application of overflushing along with pillar fracturing in a mature oilfield in Ecuador, where an effective high conductivity (high proppant concentration) fracture is required to enhance productivity because of low reservoir pressure and high permeability. Hydraulic fracturing is a proven technology used in the Oriente Basin with three challenges that remain constant (1) maximize conductivity and (2) reduce proppant flowback risk in the production stage and (3) reduce well intervention time. To address these challenges a combination of overflushed pillar fracturing, and tip screen out (TSO) are proposed. We show the reservoir analysis, laboratory tests and hydraulic fracture modeling performed to support the implementation of overflushing. Reservoir analysis includes a methodology used to execute an optimized fracture design, and laboratory tests include core flow tests that define non-damaging fluids to be used during workover and fracturing operations, and relative permeability modifiers (RPM) for water conformance. Relevant results are also presented using three key performance indicators (KPI) to evaluate the effectiveness of resin-based pillar fracturing with overflushing viz., (1) pressure buildup data (2) fluid production and (3) productivity index increase post fracturing. Three case studies are presented for fracturing candidates with special conditions, that show that this technique can be extended beyond the traditional job. Pillar fracturing (fracture and refracturing jobs) combined with overflushing in conventional reservoirs is documented for the first time, with effective stimulation results. This study applies overflushing, a practice developed for completion efficiency in unconventional reservoirs, and combines it with already proven practices in mature conventional reservoirs (pillar fracturing, customized fluids, 3D fracture design, and water conformance while fracturing) with a positive effect on production enhancement and proppant flowback risk reduction. Pressure buildup tests confirm no adverse effect of overflushing since negative skin or bilinear flow is observed, along with an increase in fluid production and productivity index in the studied wells.