Development of a novel waterflood conformance control system

Abstract

An Industry Consortium (BP, ChevronTexaco and Nalco Company) conducted a joint research project known as Bright Water. The goal of this project was to develop a novel, time- delayed, highly expandable particulate material that would improve the sweep efficiency of a water flood. In November 2001, the first of these water flood profile modification treatments was pumped in the Minas field, as reported in SPE 84897 (1). An overview of the development of the particulate system is given in the present paper. The polymeric "kernel" particles are capable of "popping" under the influence of temperature and time. The expanded particle can then provide resistance to fluid flow in porous media. Various properties of the kernel dispersions are summarized. Laboratory tests representative of the deployment of the product are presented to illustrate the injection, propagation and popping of the particles. Screening criteria for application of the product are reviewed and related to product selection for the field trial. Introduction Over the last 40 years there has been a concerted effort to improve the recovery of oil by mobility control using polymers and polymer derived gels (2). Much of the work has focussed on near wellbore gel treatments using polymers and gels but there has also been considerable work on Polymer flooding and hybrid derivatives of this (3–7). All flooding polymers alter the water mobility in the reservoir predominantly by changing the aqueous viscosity. The ratio of the apparent viscosity of the treatment (as calculated from pressure measurement during treatment injection) to the viscosity of water in the same conditions is known as the Resistance Factor (or RF). Some polymer can also adsorb on the rock pore walls to leave a lasting change through altering the hydraulic radius of the pores and thus the permeability of the rock. The ratio of the effective permeability of the rock pores to water flow before treatment to the effective permeability after flushing the treatment out is known as the Residual Resistance Factor (or RRF). The polymer flooding process has some strengths, but also a number of weaknesses. In particular the polymers are sensitive to salinity, temperature, shear and biological degradation to differing degrees. The better performing polymers tend to use more expensive monomers or production processes. There are also limitations related to the reservoir flooding process. High viscosity of the polymer flooding solution limits the injection rate at any given injection pressure. The maximum usable viscosity is typically limited to between three and ten times that of the injection water (RF maximum of 10). There are added risks of the injector fracturing and of polymer shear degradation. Unfortunately, the effectiveness of the process is reduced at low viscosity, and overall this severely restricts the range of viable applications. In the field projects where polymer flooding has been used with technical success, the cost of the accelerated oil is relatively high. In 1996 it was estimated as $8 to 10 per barrel (8) but more recently a review of the field wide commercial polymer flood in the Daqing oilfield (5) found that in this mature field, with easily accessible fresh water, the fully accounted cost was $9.34 per barrel compared with $9.42 for continued water flood production. It is apparent that a less restricted, more cost effective method for improving sweep efficiency in oil reservoirs would be desirable. This could be achieved by injecting a low viscosity material, which subsequently triggered to form a highly viscous or blocking phase. Concentrating on the permeability reduction element of the waterflood modification should result in a system that uses most of the injected materials to produce a lasting effect. It would also ensure that injected material was never subsequently produced with the water from the field. Field trials and commercial applications of gel systems intended to achieve this have been reported (9,10) but it is unclear how far the gelant penetrates into the reservoir (11).

Enhanced Oil Recovery: An Update Review

“…Documented CDG's projects include Daqing Field in China [96,102,103], El Tordillo [104] and Loma Alta Sur [105] fields in Argentina and in multiple U.S. oilfields [106,107]. Regarding BrightWater® [108], at the present time Milne Point in Alaska is the only field application discussed or documented in the public domain [109,110]. However, it is expected that the number of CDG's and BrightWater® field applications will increase in the near future based on recent field and laboratory studies underway, opening a new window of opportunities for EOR chemical methods [111][112][113][114].…”

Influence of strong preformed particle gels on low permeable formations in mature reservoirs

“…These drawbacks include the inability to control gelation time, the uncertainty of gelling due to shear degradation, gelant composition changes caused by chromatographic fractionation effect and dilution by formation water. PPG is created on the surface and injected as gel particles (Chauveteau et al 2001;Pritchett et al 2003;Frampton et al 2004;Rousseau et al 2005;Sydansk et al 2005;Bai et al 2007a, b;Zaitoun et al 2007;Wu et al 2011). PPGs are a better selection than in situ gels from the point of controlling the particle sizes for different reservoir characterization.…”

A more superior preformed particle gel with potential application for conformance control in mature oilfields

“…Preformed gels are three-dimensional, hydrophilic crosslinked polymers which, in contact with water, swell but do not dissolve as a result of a chemical or physical crosslinking and often than not will undergo a volume phase change when surrounding conditions such as temperature, salinity or pH change (Wen-Fu and Sung-Chuan 2006;Kytai and Jennifer 2002). The novelty and main difference between this technology and in situ gel technology is that with preformed gel, gel formation takes place at the surface well ahead before injection, whereas with in situ gelation, crosslinking and gel formation occur downhole in the reservoir (Bai et al 2013;Frampton et al 2004). This technology was revolutionary in that it addressed some of the problems posed by in situ gelation such as dilution and dispersion of gelant, chromatographic separation of gelant solution, dehydration, syneresis, and most importantly damage of low permeability zones.…”