Conformance Control In Reservoirs Research Articles

In situ organically cross‐linked polymer gel for high‐temperature reservoir conformance control: A review

Polymer gel has been established as water‐blocking agents in oil recovery application. In this practice, a mixture known as gelant is injected into target area and set into a semisolid gel after a certain adequate time. Besides profile modification and water shutoff, the role of the polymer gel in conformance control is to block high permeability regions, before diverting injected water from high permeability to low permeability zones of the reservoir. It is to boost the oil displacement and sweep efficiency. This is the key to improve oil recovery in the heterogeneous oil reservoirs. However, very limited gels are applicable for harsh conditions, especially in high‐temperature reservoirs. Organically cross‐linked polymer is 1 of the materials for conformance control at high‐temperature reservoirs. Many experimental works and field applications have exhibited the potential of this technology. This paper presents a concise review on this polymer gel for conformance control at high‐temperature wells. Firstly, in situ organically cross‐linked polymer gel has been introduced, and the reason of the use over other types of polymer gels is summarized. The early studies of organically cross‐linked gel systems are also discussed, followed by the chemistry and the gelation mechanisms. An extensive review on factors that affect gelation kinetics and field applications is also discussed in some detail.

An Optimization Study of Polyacrylamide-Polyethylenimine-Based Polymer Gel for High Temperature Reservoir Conformance Control

This paper presents optimization formulation of organically crosslinked polymer gel for high temperature reservoir conformance control using response surface methodology (RSM). It is always desirable to approach an optimal polymer gel formulation study with adequate performance information related to viscosity and gelation time to minimize excessive water production. In this paper, the effects of polymer and crosslinker concentrations and their influences on gelation time and viscosity were investigated. Central composite design (CCD) was used to determine the optimized organically crosslinked polymer gel formulation. Concentrations of two main raw materials, namely, polyacrylamide (PAM) and polyethylenimine (PEI), were varied in a suitable range. This was to obtain the formulation with the desirable two vital responses, which are viscosity and gelation time. It was found that the results fitted the quadratic equation. Statistically, the quadratic model is reliable and adequate perfectly the variability of the responses obtained from the experimental data. In addition, gelation time and gel viscosity may be controlled by adjusting both polymer and crosslinker concentrations. The optimum formulated organically crosslinked polymer gel with significant desirability factor conditions was achieved at 1.5% w/v of PAM and 0.3% v/v of PEI.

Experiment Study on a Novel Foam System for Enhanced Oil Recovery

Abstract. Foam, as a mobility control agent in enhanced oil recovery, is becoming more and more attractive. However, this method may be inefficient when water channeling appears in the reservoir due to its heterogeneity. Therefore, it is reasonable to block its flow through preferential channels by an enhanced foam system. A novel foam system is developed by the combination of general two phase foam system with solid particles to improve its performance for deep conformance control in reservoirs. This new foam system involves gas, liquid and particles. Firstly, micro-sphere shape and morphological distribution of particles have been observed through the microscope. Destruction mechanism and stability of multi-phase foam were analyzed in theory. In addition, the concentration of polymer and solid micro-sphere used as the foam agent were determined by orthogonal experiments. Next, micro-sphere displacement experiment shows that it can not only block throats but also migrate through throats by deformation, which can be represented by the pressure curves. Multi-phase foam system presents a similar pressure fluctuation with micro-sphere flooding. Finally, the parallel core experiments were conducted to investigate pressure distribution of two phase foam and multi-phase foam system in porous media respectively. The results show that multi-phase foam can effectively improve the profile control ability and it is adaptable for deep conformance in reservoir.