Study and Application of Formation Environment Responsive Plugging Material

The borehole wall stabilizing materials presently in use have particle sizes that are unable to accurately match the sizes of micro-fractures in the formations drilled and lack the ability to identify the formation with fractures to plug and the required selective action. A technical clue for developing formation environment responsive borehole wall stabilizing materials is presented to solve these problems. A responsive mechanism based on driving factors that are formation-related is established for the purpose of optimizing the reaction form, the morphological change of the active components in formation environment and the assembling methods of the active components and the carrier materials. Based on these studies, a formation environment responsive plugging material, SMFG-1, was developed. SMFG-1 has excellent formation responsive performance and compatibility with other drilling fluid components, it remarkably improves the quality of mud cakes, and is environmentally friendly. The pH of SMFG-1 is 6 - 8. SMFG-1 can form sediments in formation through quick responsiveness, thereby plugging pore throats and microfractures. SMFG-1 can release particles to plug microfractures with great sensitivity under controllable manner. After six pH response cycles, the release rate is still as high as 99.55%. SMFG-1 has been successfully used in drilling the complex hole section of the well Bei-XY-HF. As a result of using the SMFG-1 plugging agent, the plugging capacity of the drilling fluid was improved, and the borehole wall was stabilized. The problems encountered in drilling the easy-to-collapse hard and brittle shales with fractures and cracks were avoided and the safety of drilling the complex hole section was achieved.