Post-fracture proppant flowback has been an unwanted result of high-pressure/high-temperature hard-rock fracturing in the Mahakam river delta for a number of years, causing abundant production-related issues coupled with additional operational risks for the operator.
Previous attempts to reduce proppant flowback with resin-coated proppant (RCP) have proven to be both unsuccessful and expensive due to the brittle nature of the hardened RCP and the extended cleanout periods associated with post-job fracture cleanout using RCP in the swamp environment, leading the operator to search for an alternative solution. In early 2012, the service company implemented a new proppant flowback control service for mid- to high-temperature wells. This service has been applied to the high-pressure/high-temperature fracturing campaign in the Mahakam delta with excellent results. The service consists of a resin-coated fiber additive coupled with technical support software for design and optimization purposes. The service was pioneered on four hydraulically fractured wells throughout 2012 and 2013.
From the four wells currently treated with the new proppant flowback control service, a total of 180 lbm of proppant has been recorded at surface production facilities. All of this proppant is known to be from well A (approximately 0.18% of total proppant placed during fracture treatment). Wells B, C, and D have all recorded zero proppant returned to date. None of the four wells shows any indication of perforation burial from proppant, and there has been no decline in production that can be attributed to proppant flowback.
Over the last 30 years, an operator has been developing several fields in the Mahakam river delta, in the province of East Kalimantan, Borneo, Indonesia (Fig. 1). The fields comprise a series of interbedded deltaic sandstones, shales, coals, and, locally, limestones, with gas-bearing sand bodies, typically with a total vertical depth of less than 12,000 ft. The majority of the wells are multizone gas producers completed with cemented tubing that are perforated and produced using a bottom-up strategy.
Hydraulic fracturing operations are currently performed in two separate fields within the Mahakam delta. The fracture targets in both cases are medium- to low-permeability gas reservoirs in hard-rock formations. In this case, this is defined as reservoirs with ~1.0 mD permeability and lower and a Young's modulus of >4.0 Mpsi. The fracturing fluid utilized is a high-temperature organo-metallic crosslinked system with high-strength ceramic proppant that is used because of the reservoir and stress environment in the region.
The operator has endured proppant flowback following hydraulic fracturing in both fields. In some cases, this proppant flowback caused considerable production loss with production meeting only 20% of the full potential of the well. This is due to restrictive well choking after proppant detection, as seen in the Fig. 2 for well Z. There have been cases of both perforation burial, leading to well shut-in for cleanout and proppant production at surface. The potential of further lost production and extensive damage to surface necessitated a permanent solution to proppant flowback in the Mahakam delta.
