ANALYSIS OF SAND PRODUCTION LAW AND KEY FACTORS OF OFFSHORE WEAKLY CEMENTED UNCONSOLIDATED SANDSTONE RESERVOIRS

Unconsolidated sandstone reservoirs in sea areas are widely distributed around the world. Poor cementation can easily lead to the emergence of uncontrollable sand production during the development process, which affects the continued progress of offshore oil and gas development. At the same time, the problem of sand production during the development of unconsolidated sandstone reservoirs will also have a certain impact on the marine environment and marine life. This paper first carried out the experiment on the mechanical characteristics of the unconsolidated sandstone reservoir at sea. Then, based on the experimental data, we constructed the unconsolidated sandstone reservoir development sand production simulation analysis by using the fluid-solid coupling finite element model, and analyzed the sand production evolution law and the impact of production pressure difference on the sand production. The results of the study found that: (1) Sand production is prone to occur during the development of offshore unconsolidated sandstone reservoirs, which is usually more serious in the early stages of development. As development operations continue, the bottom hole sand production rate will gradually slow down. Under the production pressure difference of 2.5MPa, the sand production rate was 33.83g/d during 3 days of development, and then dropped to 6.970 during the 30 days of development. The drag effect is weak, and the production pressure difference is low. However, with the increase of the production pressure difference, the drag force of the reservoir pore fluid on the rock skeleton particles increases rapidly, causing the rock skeleton particles to easily break away from the sand and enter the wellbore. In order to ensure the safe development of the oil well, it is recommended that the bottom hole production pressure difference should not be higher than 2.50MPa. This study can provide reference for the design and optimization of the development plan of offshore unconsolidated sandstone reservoirs.