Research On Casing Damage Mechanism Of Steam Flooding Well Group Based On Numerical Simulation

The world's conventional crude oil recoverable reserves are estimated to be 1272×10~8m~3, while the recoverable reserves of heavy oil and extra heavy oil are 1510×10~8m~3, exceeding conventional crude oil. Since entering 21th century, China, following the United States, Venezuela, Canada, become a great power of heavy oil recovery. As the main way for heavy oil recovery at present, thermal recovery by steam injection has played an important role in enhancing recovery factor of heavy oil. However, casing damage caused by thermal recovery becomes more and more serious, and shows the trend of rapid growth. Casing damage causes the tremendous economic loss in heavy oil fields, on which the domestic and foreign experts had done a great quantity of work, but the problem has not been properly solved. Therefore, analyzing the mechanism of casing damage caused by thermal recovery is urgent to solve at present.In this paper, against the engineering background of Gudong Oilfield, based on the field data analysis of casing damage, influencing factors, formation and evolvement mechanisms for casing damage caused by steam injection thermal recovery are systematically studied, what's more, pertinence control countermeasures of casing damage are proposed. This paper carried out research in the following work:(1) Based on fluid-solid-heat coupling theory, combining subject knowledge such as thermodynamics, plastoelasticity and hydrodynamics, fluid-solid-heat coupling mathematical model has been established on the interactions of temperature field, seepage field and deformation field of heavy oil reservoir.(2) Established synthetic criterion of casing damage caused by thermal stress, taking steam drive well group as the research object, based on the numerical simulation method to study the laws of casing damage on different combinations of steam injection parameters. (3) Based on the numerical simulation results of steam drive well group, single-well fine numerical simulations have been done, studying influences of heat insulation measures on the distribution of temperature in near bore zones and formation stress field nearby borehole.(4) Studying influences of casing string stress with the variation of borehole temperature among different temperature distributions and formation stress fields.(5) In view of the perious simulation laws of casing damage, combining with oil field actual production situation, the concrete suggestions of casing damage caused by steam injection thermal recovery have been proposed.