Hydraulic Dilation Stimulation to Improve Steam Injectivity and Conformance in Thermal Heavy Oil Production

Summary In thermal heavy-oil production, steam is injected to reduce oil viscosity and promote the less viscous oil flowing to the production wells. Steam injectivity and its conformance in the reservoir greatly impacts oil production and project economics. It is found that hydraulic dilation stimulation of heavy-oil reservoirs before steam injection can create a large and targeted stimulated reservoir volume for the steam to contact the heavy-oil phase. As a result, steam injectivity increases and steam conformance improves. These eventually translate to increased oil production and reduced steam/oil ratio, which has been proven in hundreds of wells worldwide. This paper describes relevant fundamental mechanisms and field performance. As a major novelty, the hydraulic stimulation avoids fracturing the reservoir, but seeks to cause dilation. If the reservoir is fractured, a linear conduit is created. Steam can easily break through to neighbouring wells and the steam conformance is poor. When dilation takes place, however, additional pore space is created in the rock matrix. This results in truly volumetric stimulation, which is helpful to increase the steam injectivity while ideal thermal conformance is also achieved. This paper illustrates these theoretical bases and their resultant positive field performance in assisting thermal heavy-oil production.