Analysis of Geomechanical Properties in Well Design and Well Optimization
Main aspect in wellbore instability is the selection of an appropriate rock failure criterion. This criterion involves only the maximum and minimum principal stresses 1  and 3  and therefore assumes that the intermediate stress 2  has no influence on the rock strength. When Mohr-Coulomb criterion was developed it justified by experimental evidence from conventional triaxial test ( 1  > 3 2    ). Based on triaxal failure machine the Mohr-Coulomb criterion has been extensively used to represent rock failure under the polyaxial stress state ( 1  > 3 2    ). In contrast to the prediction of redistribution Mohr-Coulomb much evidence has been accumulating to suggest that 2  thus indeed have a strengthening effect. This research shown that Mohr-Coulomb failure criterion only represent, that triaxial stress state ( 1  = 1 2 3     or ) which only occasionally encountered in-situ.The linear failure criterion has been justified by experimental evidence from triaxial tests as well as polyaxial test. It is natural extension of the classical Mohr-Coulomb criterion into three dimensions. As the Mohr-Coulomb criterion only represents rock failure under triaxial stress state, it is expected to be conservative in predicting well bore instability. The 3D analytical model employed by MogiCoulomb has been achieved by using linear elasticity theory to calculate the stresses. A model was developed used in analyzing shale intrusion, at depth 6100ft the well bore pressure of the formation is found to be 0.9180psi/ft and decreases to 0.420psi/ft at depth 7300ft. The membrane efficiency of the formation increases from 0.698 to 0.719 at the depth considered above.
Coupled salt and water flows in a groundwater basin
The postulates of irreversible thermodynamics and the law of conservation of mass were combined to yield two simultaneous partial differential equations describing the simultaneous transient-state flow of salt and water in fine-grained sediments. The resulting equations have been used to analyze the movements of groundwater and salt in a subterranean aquitard in the Oxnard, California, basin, a multiple aquifer system, which has been subjected to lateral seawater invasion of an upper aquifer. Chemico-osmotic coupling may induce a small chemico-osmotic consolidation of the aquitard (0.3 mm) over a period of about 25 years, but the aquitard should act as an effective pollution barrier to the movement of NaCl into a freshwater aquifer below. The ‘tightness’ of the aquitard to salt movement depends mainly on aquitard thickness, hydraulic permeability, and drawdown in overlying and underlying aquifers.
Comparison of different antenna configurations for probing of layered media
The paper presents the results of a comparative analysis of the different configurations of antenna systems (bistatic, monostatic, differential) in terms of the simplicity and accuracy of determining the thickness of the subsurface layers of stratified environment. To this end, corresponding diffraction problems are solved by the finite-difference time-domain forward solver for each measurement setup. The analysis has shown the advantages and prospects of using differential system with vertically spaced antennas in solving of practical problems of the layered medium GPR probing.