Abstract
Abstract
Hydraulic fracturing is a common method of production enhancement for low- and mid-permeability reserves. Deep, hot gas reservoirs are usually fractured using ceramic proppant that is prone to flowback during fracture cleanup and production phases. Design techniques such as tip screenout (TSO) mode, particle size for a stable proppant arch, and choke management exist but are not foolproof. Resin-coated proppant (RCP) is a common method for proppant flowback control. However, it requires additional time and may reduce proppant pack permeability in the critical near-wellbore zone. A proppant with high aspect ratio (HARP) was trial tested as an alternative to RCP to optimize the mitigation of solids production.
Multiple repeatability long-term conductivity tests were conducted on the proppant samples. HARP was implemented in two wells replacing RCP as a tail-in proppant. HARP placement was a concern due to its size and weight; the candidate well is the deepest and the hottest well so far where HARP has been pumped globally. Therefore, the HARP concentration was limited to a maximum 7 PPA at the first trial compared to 9 PPA in the offset area with 20/40-mesh proppant. The treatment execution, challenges, performance, and solids recovery of the trial wells were compared to their offset wells using the local solids-free criteria. A novel fracture flowback simulator was used to couple fracture modeling, placement, and flowback schedule design. The numerical simulator was built by digitizing proppant pack tests to approximate the bridging and failure criteria for proppant packs.
Post-fracturing shut-in time reduction by 55% was found to be an early benefit of using HARP. The trial Well-A resulted in zero solids recovery during the post-treatment well cleanup. Following this, multiple wells were trialed with similar results except in one well that showed formation sand during flowback. In no cases was HARP recovered at surface. Offset well analysis showed higher cumulative production of proppant and formation sand, even when the RCP to total proppant ratio was two-to threefold higher compared to the ratio of HARP amount to total proppant. Also, the end-of-treatment net pressure gain increased up to 50% higher compared to the offsets. The gas production for both of the trial wells exceeded the offsets due to 50% to 900% higher conductivity, which was evaluated through long-term conductivity tests input to validate the post-fracturing net pressure history match. It was also realized that perforation strategy, including gun orientation, interval length, etc., is a critical factor for solids flowback control and must be optimized together with proppant selection. Flowback experiments with HARP showed higher critical velocity for proppant pack failure compared to RCP.
This paper presents an alternate solution for proppant flowback control material and even an alternate design strategy to integrate the flowback schedule design along with fracturing design as opposed to the silo approach. The unconventional proppant coupled with a robust flowback simulator opens high potential for unconsolidated formations. A frac-and-pack design with HARP engineering with a choke schedule has the potential to replace expensive screen completions and the complications associated with them.