Laboratory Evaluation of Placement Behavior of Microgels for Conformance Control in Reservoirs Containing Superpermeable Channels

Abstract

Gel treatment has been proven an effective method to attack excessive water production in many mature oilfields. However, not all of the application projects have successful stories. The effectiveness of a gel treatment largely depends on the transport and placement behavior of gel materials in reservoirs to be treated. In this work, we carried out systematic studies to investigate the transport, placement, water-blocking ability, fluid diversion and sweep improvement, and matrix damage effect of micrometer-sized preformed particle gels (microgels) in reservoirs containing superpermeable (super-K) channels. The impact of the channel/matrix permeability contrast and the particle/pore size ratio in the channels and in the matrices was studied. The favorable conditions for gel treatments were identified. The results show that the microgel particles selectively penetrate, place in, and effectively shut off the super-K channels under proper conditions. The sweep improvement after gel treatments was evaluated through chemical tracer tests. The results clearly demonstrate delayed breakthrough, fluid diversion, and increased swept volume of the subsequent flooding fluid. In the experiments, the sweep improvement was in the range of 0.25–0.43 total pore volumes. A higher sweep improvement was achieved as the permeability contrast was higher (i.e., the reservoir was more heterogeneous). To achieve both good injectivity and water-blocking efficiency for the tested microgels, the particle/pore size ratio in the channel should be below 2. Meanwhile, the particle/pore ratio in the matrices should be kept above 5 to avoid significant damage to the matrices. The results of this study provide support for gel product selection and successful gel treatment designs and implementations.

Progress of Research into Preformed Particle Gels for Profile Control and Water Shutoff Techniques

“…Zhao et al [ 27 , 28 ] indicated that the threshold penetration pressure (ΔPth) is a key factor influencing the selective injection of PPGs. ΔPth is the minimum driving pressure difference required for PPGs to enter channels or matrices, depending on the strength of the expanded PPGs and the ratio of particle diameter to pore size.…”

Emulsified Silica Gel for Deep Reservoir Water Conformance Control

“…They are divided into two categories based on injection strategy: in situ gels and preformed gels. Preformed gels are made up of microsized particles, pH-sensitive cross-linked polymers, swelling polymer grains, and microgels. − In situ gels are mainly made up of polymers, water, and cross-linking agents. − Colloidal dispersion polymer gels (CDGs) are types of in situ gels in which a lower concentration of polymer is used with a cross-linker that can penetrate deeply into the high-permeability zones without damaging the lower permeability oil zones. The CDGs have been criticized in a review by Wang and Seright that they do not propagate deeply into the reservoir and provide resistance factors that are greater than the same polymer without a cross-linker.…”

Experimental Investigation of a Novel Nanocomposite Particle Gel for Water Shutoff Treatment in Mature Oilfields

“…Many oilfields have entered the stage of high water cut with the further development of oilfields. Chemical water shutoff, as a cost-effective technology, has become the main method for enhancing oil recovery in mature oilfields. − As the water shutoff technologies developed, petroleum workers have developed different types of plugging agents, such as in situ polymer gels, − preformed particle gels (PPGs), − and so forth. In situ polymer gels were cross-linked polymer gels (CPGs) composed of polymers and cross-linkers.…”