Strength prediction of weakly cemented sands from geophysical logs
This dissertation comprises five manuscripts resulting from a study on a critical problem in the oil industry called "Sanding". Sanding is a phenomenon in which sand from a formation is drawn into a well during production and pumped along with oil and gas. This occurs in weakly cemented sands and sandstones, and can cause significant damage, including erosion of pipelines, loss of production, and in extreme cases the loss of oil wells. A knowledge of the strength of these formation is critical for the effective analysis of sanding potential and design of possible preventive measures. ^ The objective of this research is to develop a practical tool for estimating the strength of weakly cemented sands (i.e. unconfined compressive strength, real cohesion, and friction angle) from commonly measured geophysical logs (compression wave velocity, shear wave velocity, and porosity). To achieve this, an extensive laboratory testing program was conducted on artificially cemented samples of varying densities and levels of cementation. Geophysical measurements on these samples included bulk density and shear wave velocities. The laboratory testing program included triaxial compression tests, unconfined compression tests and indirect tension tests. Real cohesion and tangential friction angles were estimated using a nonlinear Mohr envelope. ^ Based on the laboratory results, four empirical models were developed that related small strain shear modulus or compression/shear wave velocity ratios with shear stresses at failure. Because in situ logs are influenced by environmental conditions, and pore fluid composition, a methodology was developed to estimate strength from synthetic velocities. This methodology has the potential to estimate the unconfined compressive strength, and real cohesion of weakly cemented sand directly from field measured porosity and compression wave velocity logs. ^
Geotechnology|Engineering, Civil|Engineering, Marine and Ocean
Ravi Sharma M. Srinivasan,
"Strength prediction of weakly cemented sands from geophysical logs"
Dissertations and Master's Theses (Campus Access).