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Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Drilling Fluid & Completion Fluid is the property of Drilling Fluid & Completion Fluid Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Research shows that there is no equipment for simulating the mud loss zones in fractures and vugs with active water. Based on the investigation and study on the characteristics of the mud loss zones in fractures and vugs with active water, the functions to be achieved and the corresponding parameters of the simulation apparatus were clearly defined, and the structure and components of the apparatus were determined. The simulation apparatus is composed of five subsystems, which are the fracture and vug simulation subsystem, the formation water simulation subsystem, the lost circulation material slurry injection subsystem, the borehole simulation subsystem and the data acquisition subsystem. This simulation apparatus can be used to simulate a water flowing speed of 10 m/min and has a pressure bearing capacity of 2 MPa, satisfying the needs of controlling mud losses into most fractures and vugs with active water. Using this apparatus, the factors affecting the retention of gel in mud loss channels with active water were evaluated. The test results show that in a mud loss channel with atmospheric pressure, good retention of the lost circulation control gel can be obtained at the following conditions: the injection rate of a lost circulation control gel is greater than 1.2 times of the water flowing rate, the adhesion strength of the gel is greater than 10.1 N/m², and the density of the gel is between 1.1 g/cm³ and 1.2 g/cm³. This study has provided a guideline to the control of mud losses into fractures and vugs with active water. [ABSTRACT FROM AUTHOR]

In recent years, many wells in Shunbei oil and gas field have encountered serious wellbore collapse due to drilling in broken formation, resulting in frequent jamming and many wells backfill sidetracking, which has become one of the major technical problems in the exploration and development of Shunbei oil and gas field. Statistics and analysis on the complicated situation of Ordovician broken formation in Shunbei oil and gas field were made. In view of the technical difficulties in the broken formation, the collapse and instability mechanism were studied and analyzed, and the technical measures for safe drilling were put forward. The results show that the instability mechanism is mainly affected by the extrusion structure, the stratum is broken and the stress is concentrated. In addition, the weak planes such as high angle micro fractures and bedding are developed, and the cementation is poor and the structure is loose. It is easy to shear failure and cause large area collapse and instability. The drilling fluid should strengthen the sealing and consolidation properties, improve the formation integrity and rock strength, appropriately increase the drilling fluid density, strengthen the mechanical support, and improve the carrying capacity of drilling fluid to keep the borehole clean. In order to ensure downhole safety, when drilling in broken formation, drilling tools should be simplified as much as possible, drilling parameters should be optimized, drilling strategy should be“less advance, more retreat”. [ABSTRACT FROM AUTHOR]