نشریه روش های تحلیلی و عددی مهندسی معدن
پیاپی 1 (زمستان 1389)

Based on the extensive studies, undoubtedly, the role of the shear wave data in hydrocarbon reservoir evaluation is vital. Using shear wave along with P-wave data often allows us to identify the seismic signatures of lithology, pore fluid type and pore pressure, efficiently. Unfortunately shear wave data is not available in all reservoirs and it is necessary to predict it. This study has done on a well in one of the oil reservoirs in south of Iran that has shear wave velocity measurements. In this study shear wave velocity had predicted by rock physics relations and neural networks and then the results compared with real shear wave velocity measurements. Regression between predicted shear wave velocity by using rock physics relations and measured shear wave velocity is about 0.91, whereas it is about 0.95 by using neural networks. Results confirm that both methods are suitable for predicting shear wave velocity in other wells in this reservoir.

Concrete liner of excavations in swellable rocks is under time dependent stress. One of the most famous methods for determining the stress is compensation method using flat-jacks. As the first step، measuring pins are cemented on the surface of the concrete lining in an appropriate arrangement on both sides of the planned cut. The distances between the pins are recorded by an accurate displacement sensor. Following the zero measurement، a slot is cut with a diamond-tipped circular saw blade. Hydraulic pressure cell (flat-jack) is inserted into the slot and is connected with a hydraulic pump fitted to a precision manometer. Finally، the flat jack is loaded until the relief-induced deformations are compensated. Since swelling is a time dependent behavior، the stress of liner changes with time. This needs a periodic measurement using heavy pumping device and requires a time consuming process. In this paper، the ability of adaptive network based fuzzy inference system is examined to predict the mentioned stresses. The performed compensation test at Masjed-Soleiman underground power house has been used as an example to illustrate the method. Using this method an engineer is enabled to predict the lining stress by reading the slot closure across a flat jack device.

Salt domes are one of the most important oil traps. More over salt minerals can be present in other oil traps. Drilling in salt formations can result in many problems such as stuck pipe of drilling strings and casings، closure of borehole’s wall and therefore bad cementing and casing failure. These problems occur as the result of creep phenomenon which is the time dependent deformation of salt under constant stress. The aim of this paper is to study the mechanical behavior of salt rock. Based on obtained results، appropriate drilling fluids، the time for running the casing in the borehole، and the collapse pressure on the casing can be determined. The effect of drilling fluid’s weight on reducing the rate of borehole’s wall closure is evaluated by FLAC codes. Considering that drilling of oil and gas wells is an expensive operation، optimization of the drilling fluid''s weight can ensure oil well integrity. Heavier drilling fluids can reduce the rate of borehole’s wall closure and therefore the running of casing can be postponed.