When the formation is unconsolidated, sand particles can be produced into the wellbore. Such production of sand particles is undesirable as it lowers the permeability of the producing zone, erodes surface and downhole equipment. Costly intervention may be required to mitigate the damage to the well integrity and the reservoir deliverability. The most common methods of controlling this unwanted sand production involve: 1. Filter produced fluids through a gravel pack retained by a screen or 2. Use of consolidating fluids such as resin, a curing agent, along with other chemicals to create a conducive environment for the resin curing reaction to occur. The gravel packing completion requires special tools and equipment therefore higher cost. In the case of sand control by chemical consolidation, the resinous material tends to have relatively uncontrollable setting times, strength, placement, and regained permeability leading to unsuccessful treatment. With both cost and treatment effectiveness in mind, it is desirable to develop an improved material and method to mitigate sand production by consolidating the formation sand without impairing well productivity or injectivity.
The present paper describes the development of a unique chemistry for sand control in unconsolidated formations. This chemistry involves using positive charge modified nanoparticles that can self-assemble over the unconsolidated formation sand particles 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 ionic strength modifier that can be placed downhole as a single pill. The pill 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 produced hydrocarbons or injected water.
The newly developed sand consolidation formulation was studied for their ability to consolidate loose sand and at the same time maintain good permeability. The effect of various ionic modifiers on consolidation properties was studied. 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 good regain permeability of the consolidated sand pack. Furthermore, this paper describes the concentration effect of the cationic modifier on the regain permeability. Finally, it shows that the new product provides a controllable curing time, thus avoiding any premature setting of the nanoparticles in the wellbore.
