Sanding in hydrocarbon producing and water injection wells has been a severe problem in unconsolidated formations. Many technical solutions have been evaluated by the industry. These solutions encompass mechanical sand exclusion methods such as screen, gravel packing, and frac and pack. Various production and completion practices such as controlling the production rate and following specific well completion guidelines to minimize sand production have failed to provide satisfactory returns. Several limitations such as screen plugging and high costs associated with deploying expandable screens make the current mechanical sand control practices more expensive. With both cost and treatment effectiveness in mind, chemical sand consolidation could present the most cost effective remediation and prevention opportunity. Additionally this would also allow the wellbore to be free of tools, screens and pack sands.
In this paper we describe the development of a unique chemistry for mitigating sand production in unconsolidated formations. This chemistry involves using cationically-modified nanoparticles that can self-assemble over loose formation sand to form a layer of consolidating material thus preventing any unwanted sand production. The new consolidation treatment material consists of colloidal nanoparticles modified using a cationic modifier and oligomeric activator that is initially low viscosity fluid. The fluid has high affinity to the solid surface therefore less prone to build up in the pore space. Once cured at reservoir temperature it forms a thin layer of hard gel around the surface of the sand particles, thus cementing the sand grains together at the same time maintaining open porosity to ensure easy flow of hydrocarbons and injected water.
The ability of the new fluid to consolidate loose sand and at the same time maintain good permeability was investigated. Various oligomeric activators were studied with particular focus on effect of concentration temperature and shear. The ability of the cationic modified nanoparticles to self-assemble around unconsolidated sand and eventually cure to form a consolidated sand pack was investigated. Regain permeability studies showed excellent regain permeability of the consolidated sand pack. It was also shown that the new sand control fluid system provides a controllable curing time, thus avoiding any premature setting of the nanoparticles in the wellbore.
The novelty of the newly developed sand consolidation system is its ability to self-assemble around unconsolidated sand and eventually cure to form a consolidated sand pack while maintaining good permeability.