Low Solids Shear Dependent Fluid System to Plug Zones for Preventing Fluid Influx and Loss

Abstract

Abstract Lost circulation and influx from sections of high-pressure zones is a recurrent challenge and high-cost event within the oil industry, particularly in mature fields or weak-fracture-gradient zones. These can significantly increase operational costs, non-productive time (NPT), the possibility of stuck pipe, and well integrity challenges. Lost circulation can be defined in a variety of ways, from partial to total loss, and in a variety of formations, including highly-permeable, fractured, or cavernous formations. Loss circulation materials, such as particulates, have been successfully used to plug smaller fractures and permeable zones. Challenges arise when the losses cannot be stopped using particulates because of the loss magnitude. The industry has used various chemical solutions to overcome this challenge with mixed results. Particulates are usually unsuccessful in terms of plugging high-pressure zones to help prevent fluid influx. This paper presents a low-solids loss circulation solution that develops rapid gel strength when shear rate decreases. The gel strength buildup is based on polymers and nanomaterials in the fluid system. This helps prevent fluid from continuously flowing into the zone or being expelled from the zone. Once gel strength has developed, the system develops nominal compressive strength to adhere to the formation and thus helps prevent displacement during subsequent well operations. The fluid is shear thinning and hence easily enters the formation zone and does not flow continuously, as it gels upon entering the formation. The low solids and low rheology under shear means that it can be easily pumped through the drill bit without having to pull out of the hole (POOH). This paper describes a system that was pumped into a high-pressure zone to isolate an unconsolidated sand formation. Initial attempts to isolate the zone included a bradenhead squeeze operation, which was unsuccessful, and fluid influx from the zone was observed during subsequent well operations. The fluid system and process described in this paper should help the industry in terms of shutting off streaks of high-pressure zones and curing fluid lost into the formation.