Design Considerations of Waterflood Conformance Control With Temperature-Triggered, Low-Viscosity Submicron Polymer

Abstract

In waterfloods, the existence of highly conductive thief zones causes poor volumetric sweep efficiency, resulting in early breakthrough and excessive production of water. A conventional strategy of redirecting injection by closing off perforations yields short-term benefits because diversion occurs near the wellbore. As an alternative, temperature-triggered submicron polymers with low viscosity (popping agents), which give an opportunity for conformance control deep in the reservoir, have been introduced in recent years. This technology aids conformance control by plugging the high-permeability zones and diverting the fluid to the unswept portion of the reservoir.Understanding the critical parameters that lead to a successful treatment and accurate determination of the slug size are two important criteria for a technically and economically successful treatment. In this study, we first investigate the effect of different parameters on the success of a conformance control treatment. A comprehensive design-of-experiments (DOE) study resolves the effects (and combined effects) of k v /k h , treatment fluid concentration, thief-zone to matrix-permeability ratio, mobility ratio, and location of the placement in the reservoir. Next, a methodology is developed for accurate determination of the conformance slug size. The method is built on the temporal moment and residence time distribution analysis (RTDA) of interwell tracers. Dynamic flow-and storage-capacity curves are used to identify the optimum slug size.3D thermal computer simulations show that thief-zone to matrix-permeability ratio and placement location of the polymer are the most important parameters that affect the success of a treatment. The most desirable setting is placement of the polymer deep in the reservoir, closer to the producer within high k v /k h reservoirs. Furthermore, the computer simulations confirm the power of the new technique for optimal slug-size determination. This new technique can avoid underestimation of the volume that must be treated, which is critical for the success of a treatment.

A critical review on use of polymer microgels for conformance control purposes

“…Unlike PPGs, BrightWater is not intended for use in fractures (Mustoni et al, 2010;Pritchett et al, 2003). Different BrightWater grades are available for systems of different temperatures and/or different desired thermal reaction rates (Garmeh et al, 2011;Husband et al, 2010;Izgec and Shook, 2012;Ohms et al, 2009;Yanez et al, 2007). Activation/ triggering temperature of the BrightWater particles depends on the crosslinker selected and its associated mechanism of decrosslinking for swelling (Chang et al, 2002;Frampton et al, 2004).…”

“…BrightWater has also been used in the Salema field in Brazil (Roussennac and Toschi, 2010) and in the El Borma field in Tunisia (Ghaddab et al, 2010). Garmeh et al (2011) and Izgec and Shook (2012) are useful references for those considering BrightWater technology. Garmeh et al (2011) present a workflow for BrightWater treatment design and evaluation, and also discuss different simulation approaches to evaluate the effects of treatment concentration, slug size, permeability contrast, k v /k h , mobility ratio, and gel activation location.…”

“…Garmeh et al (2011) present a workflow for BrightWater treatment design and evaluation, and also discuss different simulation approaches to evaluate the effects of treatment concentration, slug size, permeability contrast, k v /k h , mobility ratio, and gel activation location. Izgec and Shook (2012) also carried out a similar simulation study, and determined that gel placement location and permeability contrast (between the thief zone and surrounding layers) are the most important factors determining the success of a BrightWater treatment. Izgec and Shook (2012) also presented an approach for determining the slug size of a BrightWater treatment.…”

“…Izgec and Shook (2012) also carried out a similar simulation study, and determined that gel placement location and permeability contrast (between the thief zone and surrounding layers) are the most important factors determining the success of a BrightWater treatment. Izgec and Shook (2012) also presented an approach for determining the slug size of a BrightWater treatment. Onbergenov's (2012) work can be referred to for additional insight obtained from BrightWater simulation sensitivities.…”

Reservoir In-Depth Waterflood Conformance: An Offshore Pilot Implementation

“…Effects of TAP adsorption was also evaluated through detailed sensitivity analysis during the simulation study conducted as part of Ebano pilot design. TAP pilot design in Ebano was supported by detailed numerical simulation studies following simulation approaches reported by Garmeh et al (2012) and, Izgec and Shook (2012). The first step was to confirm that the available and history matched black oil model represented the observed water injection profile (PLT at 6,000 bbl/d) before its conversion to compositional/thermal model.…”