Investigation of LCM soaking process on fracture plugging for fluid loss remediation and formation damage control

Abstract

When drilling through naturally fractured reservoirs, the remediation of drill-in fluid loss needs to be designed by taking both fracture plugging and formation damage into account. Lost circulation materials (LCMs) should be implemented efficiently to minimize the solid-laden fluid invasion into the fractures during the development of fracture plugs. This study investigated the effects of three LCM deployment factors: injection rate, soaking time, and soaking pressure, on the total fluid invasion volume and plug breaking pressure. Full factorial experimental design and statistical analysis were conducted to study the statistical significance of each factor. Scanning Electron Microscope (SEM) and Micro Computed Tomography (MicroCT) were applied to visualize the plug structures for the understanding of the soaking effects.Different combinations of LCMs were tested in a permeability plugging apparatus with a slotted disk. For granular LCM mixtures, the soaking pressure and time did not have a significant impact on total fluid invasion volume or ultimate plug breaking pressure. For mixtures blended with fibrous LCMs, longer soaking time contributed to reducing fluid loss and increasing plug breaking pressure. A lower LCM pill injection rate led to less fluid invasion upon the establishment of an effective seal. The SEM and MicroCT images indicated that a longer soaking time could lead to a less porous and strengthened plug structure.The results and conclusions from this study provide new insights into the identification of optimal LCM implementation scheme with better formation damage control.