Optimisation of Sand Control Technique for Offshore Heavy Oil and Unconsolidated Sandstone Reservoir: Case Study from Bohai Bay

Abstract

Abstract As conventional hydrocarbon resources in current basins of the world continue to decline, heavy oil becomes a significant candidate to fulfill the world's thirst for energy. In China, the potential reserves of heavy oil amount to 220 billion BOE, with more than 13% in offshore fields. For Bohai Bay, up to 80% of developed reservoirs are heavy oil and unconsolidated sandstone reservoirs. Due to the geological process and depositional environment in generating heavy oil, the common characteristics of such oils are high viscosity, low gravity, high asphaltenes, and weak homogeneity and cementation. As a result, the productivity of heavy oil is usually low in a single well, accompanied with sand production. In recent years, the sand control customization technology and single well precise design based on single formation was developed to optimize deliverability of single formation. The optimized sand control technique has become one of the major methods for increasing and stabilizing production in Bohai Bay offshore oilfield. This paper begins with an introduction of the application and limitations of traditional sand control methods in Bohai Bay offshore oilfield. Then, to meet the requirement of further enhancing oil recovery, sand management and proper sand control completion technology are introduced. After the experiment was conducted, the results of sand control were obtained from most oilfields. However, bad results of application still existed in some oilfields. Introduction Up to 80% of developed reservoirs in Bohai Bay are heavy oil and unconsolidated sandstone reservoirs. The restrictions - such as the wide range of reservoir distribution, shallow depth, poor diagenetic grade, and sand production - become principal obstacles for reservoir development. According to official statistics, up to 90% of wells in Bohai Bay need sand control. The effect of the sand control will directly affect the enhanced oil recovery. Traditional sand control methods cannot satisfy the requirement of better enhanced oil recovery since the most of oilfields in Bohai Bay are characterized by high oil viscosity, sand production, high asphaltenes and resin content, and weak homogeneity and cementation. Since 2002, operators have applied the sand management concept and sand control completion technology to multiple oilfields with enlarged production pressure differential and expansion of well production capacity. Under the above circumstances, the sand production has been controlled within the scope of the security. It has been proven that the sand management concept and sand control completion technology have successfully controlled sand production in most oilfields. But for a few low-pressure heavy oil reservoirs, the results have been poor. In 2008, the optimized sand control technique, which can maximize every formation's production capacity and control sand production at the same time, became one of the key measures of oilfield production stabilization and stimulation.