Associative Polymer Usage as Stimulation Diversion System for Multilayered Reservoirs: Case Study of its Effectiveness for Stimulating Tight Layers in Khuff Carbonate Formation from Saudi Arabia's Ghawar Field

Abstract

Abstract Acid fracturing as stimulation treatment for lower permeability multilayered reservoirs has been extensively used for carbonate formations around the world. For multilayered reservoirs, the success of stimulation is highly dependent on the fracture capability to connect the layers, fluid leak-off, fracture geometry and stimulation fluid properties. In Khuff carbonate reservoir from Ghawar Field, the heterogeneous nature of the multilayered formation, temperature, layers separation and especially wellbore deviation along the interval to be stimulated present additional technical challenges for fracturing stimulation and all of them has been addressed by incorporating Associative Polymer blends as a separate step to assure an effective fracturing stimulation fluid diversion. The paper will show a case study for gas well in Ghawar field where an effective diversion technique with Associative Polymers was used successfully in fracturing treatments which resulted in enhancing more of tight layers contribution and increased total productivity by more than an order of magnitude. Associative Polymer (AP) blended in an innovative way forming, a solids or fibers free non-reactive water base system. The new diversion system was successfully used in several gas wells completed in Khuff carbonate reservoir where clear diversion and acid reaction signatures have been implied by surface and bottom-hole pressure (BHP) data recorded during the entire treatments. Production increases in addition to Pressure Build-up (PBU) and Production Logging corroborated the flow contribution from all the perforated intervals included tight layers, which contrasts with offset producers previously treated with other types of diverting agents. The paper will present for the first time the treatment design and benefits of AP blend diverting agent usage for acid fracturing stimulations. A case history where the wellbore orientation is 45 degree is going to be presented and discussed in detail. Field case shows that the wellbore deviation was not a limitation for the effective stimulation and for the AP blend system to work. In addition, this paper will provide some guidelines for potential use of this diverting agent and candidate selection, treatment design, and execution.