Development of responsive well plugging material in carbonate reservoir

Abstract

One of the most critical problems limiting the exploration and development of the Central Asia and Middle East Areas is lost circulation caused by the natural fracture propagating in carbonate reservoir. Traditional plugging materials had limited performance due to poor adaptability to carbonate formation. This paper investigated the mechanism of lost circulation in Central Asia and Middle East Areas, and a new responsive fracture plugging materials was developed. After implementation, the complexities treatment time was shortened and drilling efficiency was increased. The main types of lost circulation mechanism are summarized and analysed by studied the reservoir characteristics of Central Asia and Middle East Areas. A physical model of horizontal V funnel leakage channel in the target block was established to simulate the migration and plugging process of plugging particles in natural fractures. Based on the analysis of the flow and accumulation pattern of the plugging fluid in the leakage channel with different aperture ratio, a statistical model of the particle flow in the plugging material was established. A response controllable solidification plugging material was developed. The application results show that, the responsive solidification controllable well plugging material could rapidly accumulate in the 1mm and 3mm fractures in the upper sealing formation. The mud cake has good toughness with compressive strength of 3.4-9.5MPa, which achieves a rapid and high-strength plugging for the fracture formation. The acid soluble consolidation plugging material, mainly composed of curing agent, retarder, suspending agent, etc., is developed for long open hole section. The dissolution rate could reach up to 91%, the plugging strength of the solidified plug is up to 10MPa and which could be stable for 15d under 150°C. This innovative anti-lost circulation materials for carbonate reservoirs can effectively solve the problem of serious loss of production due to sever lost circulation problem in the Mishrif reservoirs of Central Asia and the Middle East and enhance the drilling of complex carbonate oil and gas fields. The implementation of this plugging material improves the technical level of drilling and completion of complex carbonate oil and gas fields and provides strong support for exploration and development in Central Asia and the Middle East.