Sand Control Mechanism And Technology Research Of Self-adapted Expandable Sand Control Screen

Sand production becomes a generally problem encountered in oil and gas wells. It has affected the normal development of oil and gas reservoirs. How to develop the new equipment to prevent sand production, how to prevent and control sand production effectively, and how to lower operating costs, have become a race-related issue for scientific research institutions.The sand-production simulation experiments are finished based on the analysis of sand production mechanism and influencing factors. The result shows that the drive pressure variety gave little affection to sand production. The capacity of sand production have little increase with the addition of water content, and sand production is occurred at the beginning of water appeared. When the critical pressure is 2MPa and critical fluid velocity is 7ml/min, sand production is increased largely. The yield of wells and sand production are all increased with the accretion of fluid velocity.The structure of self-adapted expanding screen is designed based on the concept of particle expansion and the combination of hardness and softness. The new type of screen is made up of protective outer shell, expandable mesh, gravel pack layer and the slotted screen as the base pipe. The parameters of the base pipe like tube wall thickness, slot length, slot width, slot distribution form, slots distribution density and other parameters are considered for the design of the base pipe based on the self-developed software (SFEM). Also, the relationship of the above parameters and the stress of the base pipe is analyzed and summarized. Meanwhile, mesh combination structure between the layers were analyzed, a reasonable design of screen mesh size is proposed.The high pressure liquid carrying gravel fills the space between base pipe and expandable mesh and the soft expansion is completed. The "zero annulus" for irregular borehole section of the well and uniform expansion pressure is achieved by one expansion process. The screen expansion mechanism is researched and the new pressure drop formulation is deduced and used to calculate the pressure drop of the expansion layer base on the conical flow model. The filling pressure, fill thickness and filling gravel size are optimally chosen base on the calculation results. The research show when the gravel packing pressure is about 15-20MPa, the thickness of gravel packing zone is about 25-30mm, the gravel-to-sand median diameter ratio is about 7,the screen can attain the best pccking effect.The compound sand control system is new type of screen is made up of expandable mesh, gravel pack layer and the slotted screen, and it made a good sand control effect. The flow experiments, optimal parameters chosen experiments and sand prevention effects experiment are carried out using the self-developed sand control simulation equipment. The BP neural network model for the sand control method chosen is established and the specific examples are used to carry out calculation for the optimally chosen. The sand control effect is comprehensive evaluated from five aspects of sand control function, yield increase, availability time, flow condition improve of well bottom, benefit of sand control.The erosion mechanism and corrosion mechanism of base slotted pipe are analyzed on the erosion experiment and corrosion experiment using the self-developed test simulation equipment. The research shows that the erosion is serious with the increase of fluid velocity and impact angle. When the sand particle size and sand concentration are increased, the erosion quantum is increase at the beginning, and then decreased. The surface corrosion rate is expedited with the temperature increase during 30 oC～80 oC, it reach the highest spot at 80 oC and then declined. The screen surface occur dot-corrosion easily in solution which contain chlorine ion, corrosion rate decline with the concentration increase of chlorine ion. The calcium ion can restrain the screen surface corrosion rate. Corrosion rate is decline with the pH value increase during the pH value of 3～6.