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.
Evaluation of Spotting Fluids in a Full-Scale Differential Pressure Sticking Apparatus
This paper reports that a full-scale differential-pressure simulator was used to evaluate spotting fluids in the laboratory. Tests at elevated temperature and pressure identified a variety of unweighted and weighted, oil and nonoil fluids that are able to free differentially stuck pipe. Some low-toxicity, water-based spotting fluids are effective and acceptable substitutes for the traditional oil-based systems.
An operational method for estimating signal to noise ratios from data acquired with imaging spectrometers
A method, using the concept of local means and local standard deviations of small imaging blocks and using a box counting procedure, has been developed for unsupervised estimation of the average signal to noise ratios of images in which the noise is additive. The method has been applied to simulated images with Gaussian noise, to images acquired with the Airborne Visible Infrared Imaging Spectrometer and with the Geophysical and Environmental Research Imaging Spectrometer. The method is compared with other techniques for estimating signal to noise ratios from imaging data. It is believed that the method is generally applicable to images having many small homogeneous blocks. Because the method does not take into account interband effects, it is not appropriate to use the method to estimate signal to noise ratios from images having nonnegligible interband radiometric calibration errors at spatial scales less than or equal to the size of the small imaging blocks used in the noise estimation.