The Complex Lithologic And Stratigraphic Borehole Stability In Deep Areas Of The Great Northern Grams Logging Evaluation

DaBei and KeShen area in Tarim basin is characterized by complex geological structure, strong crustal stress, complicated formation lithology, tight reservoir, and poor physical property.Moreover, exploration wells are ultra deep, temperature and formation pressure are very high, and existing multiple pressure regime. During the well drilling process, the borehole stability is poor, the borehole collapse and mud loss are seriously. Analyzing the borehole stability of the work area is a premise to ensure the scientific drilling. These problems would affect the drilling speed, quality and cost. What's worse, it couldn't reach the target stratum because of the borehole instability in some new exploration area, which would affect the process of exploration and total economic benefit.Considering the advantages of logging method in the drilling engineering, such as continuity, high resolution and economy, the author made lots of research on borehole stability in DaBei and KeShen area, the main researches are as follows:(1) Based on the formation characteristics and rock core data of Paleogene system and Cretaceous to establish the pattern of porosity, permeability and saturation.At last, made interpretation of formation lithology profile, physical property profile.(2) Extracted the S-P slowness, F-S shear-wave slowness and azimuth information from the array sonic logging data, and interpreted the rock mechanical parameters and crustal stress anisotropy. According to the rock mechanical test data, established Static Conversion formula for Young's modulus and Poisson's ratio, and set up rock mechanical parameters profile of Paleogene system and Cretaceous formation in designed area.(3) Optimized the pattern to calculate the crustal stress, formation pressure, caving pressure and fracture pressure, and finaly established their profile and analysed the longitudinal distribution characteristic.(4) Combined with the rock mechanics, crustal stress and formation pressure, caving pressure and fracture pressure profile, according to Mohr-Coulomb yield criterion, started from borehole stability to analyse the mechanism of borehole collapse and mud loss in the clastic rock formation. Furthermore, based on the logging data to identify the easily borehole collapse and mud loss formation.(5) According to the longitudinal distribution characteristic of formation pressure, caving pressure and fracture pressure, combined with actual drilling data to set up the security mud density window.(6)Based on above researches, a borehole stability of logging evaluation software is programmed specific for DaBei and KeShen area by virtue of Forward.net platform, Fortran programming language.Based on above researches, a borehole stability of logging evaluation software is programmed specific for DaBei and KeShen area, which can be used to accurately calculate formation pressure, caving pressure and fracture pressure, even set up the security mud density window.Considered the approved results of well-logging data processing, it can be used to guide the etroleum engineering design and the construction.