Conformance Control Treatments for Water and Chemical Flooding: Material Screening and Design

Abstract

Heterogeneities in the reservoir can result in poor sweep efficiency during water and chemical floods. In many cases the sweep efficiency is improved significantly when changing to polymer flood. However, in the presence of very high conductive features polymer by itself may not be sufficient and result in undesired polymer production. Diversion of the flow to oil saturated regions and minimization of polymer production is then desired. In the presence of cross-flow the best option is placing a (chemical) plug deep in the reservoir. Adding a second component to the injection polymer stream that can react with the polymer to form a cross-linked gel is then an effective solution. However controlled placement and triggering of the reaction is very challenging. In this paper we will present the results of static bulk measurements and dynamic core flooding experiments that were performed to identify cross-linked polymer systems. The polymers in the system are the typical high molecular weight partially hydrolyzed polyacrylamide (HPAM) polymers used in polymer flooding projects. The experimental work is focused on understanding and controlling the gelation time to enable proper placement and triggering at any given distance from the injectors. Parameters of investigation included temperature, brine composition, polymer concentration and rock mineralogy. The main parameters affecting the gelation process and possible failure mechanisms were identified. For given conditions, retardation of gelation time varying from few days up to several months could be designed. The learning from the experimental results can be used for improved material selection and design for other chemical and water flooding.

Fabrication and evaluation of hydrophilic cross‐linked polystyrene nanoparticles as a potential in‐depth conformance control agent for low‐permeability reservoirs

“…5,6 For most low-permeability reservoirs, the characteristics of strong heterogeneity and fracture development in the geology, leading to the injected flooding fluids breakthrough prematurely, thereby a great deal of oil-bearing areas are inaccessible and low oil recovery. [7][8][9][10] In-depth conformance control has been generally acknowledged as one of the most feasible technology to address the breakthrough issue. Conformance control agent is the essence of this technology.…”

“…The oil recovery of reservoirs mainly depends on the volumetric sweep efficiency and oil displacement efficiency of flooding fluids 5,6 . For most low‐permeability reservoirs, the characteristics of strong heterogeneity and fracture development in the geology, leading to the injected flooding fluids breakthrough prematurely, thereby a great deal of oil‐bearing areas are inaccessible and low oil recovery 7–10 . In‐depth conformance control has been generally acknowledged as one of the most feasible technology to address the breakthrough issue.…”

Flow of a Cross-Linking Polymer in Porous Media

“…In-depth profile modification is a promising technology for improving the sweep efficiency of water flooded heterogeneous oil reservoirs (Seright et al 2011;Sydansk and Southwell 2000;Bailey et al 2000;Glasbergen et al 2014). It can be implemented by injecting a crosslinking polymer (XL polymer) that propagates deep into the reservoir.…”

“…2). The efficiency of the process depends on the geological characteristics of the reservoir, the physical properties of the cross-linking polymer, its concentration in the target zone and the interaction with the minerals of the rock (Seright et al 2011;Bailey et al 2000;Glasbergen et al 2014;Lake 2010). The most appropriate chemical system for in-depth profile modification in a reservoir should have the following properties: tolerance to the salinity of the brine, thermal stability, low initial viscosity, deep propagation into a reservoir, and low mechanical degradation (Karsani et al 2014;Zhang and Zhou 2008;Zitha et al 2002).…”

“…Therefore, it is important to study the in situ dynamic cross-linking of polyacrylamide both from a theoretical as well as from a practical point of view. Cross-linking of HPAM often happens fast (2-4 days) (Glasbergen et al 2014). In general this is not acceptable for the purpose of injecting a XL polymer deep into a reservoir.…”