Laboratory Rock Characterization Study for Optimized Sand-Control Completion Using Samples Selected from Pre-Khuff Reservoir

摘要

The production of sand into the wellbore is one of the oldest problems in the oil and gas industry. The produced sand could lead to plugging-off the wellbore, erosion of surface equipments, and the settlement on the surface facilities. There are two options currently available to control the sand production: (1) restricting the production rate and ultimately controlling the drawdown pressure that will cause the load-bearing formation from failing at higher stress. (2) Using mechanical/ chemical ion control techniques to prevent the formation sand from entering the wellbore. This study focuses on investigating the role of rock mechanics, particle size distribution and characterization study for sand control completion. The Knowledge gained from the investigation will be used to build up in-house know-how and skills which enable the setting of new guidelines for evaluating and designing of the best type of sand control techniques. An integrated approach was applied to investigate the role of rock mechanical properties, sand texture, particle size distribution and location of clays materials within the pore structure in sandstone samples selected from Pre-Khuff reservoirs. Ultrasonic compressional and shear velocities were measured on each sample and dynamic Young’s modulus and Poisson’s ratio were obtained. Eight representative samples were selected from the wells under study for mineralogical characterization and for identification of the clay types and their distribution within the samples by using X-ray Diffraction (XRD) and Environmental Scanning Electron Microscopy (ESEM) analytical techniques. Dry sieve analysis and ESEM were also conducted on samples selected from various depths. In addition, porosity and permeability measurements were conducted on the samples. The results, showed that porosity level ranges from 29%- 4.0% and permeability ranges from 968 - 0.1md. The XRD analyses conducted on the samples indicated the presence of Dolomite, Microcline and their disappearance, which has more cementing characteristic compared to other minerals. The grain-coating cement was evident; this provides a significant cementation to the grains and tends to have more strength and high friction angles. The samples tested from some of the wells follow the reported relationship between unconfined compressive strength and porosity. There is inverse relationship between these two important properties. This relationship will provide us with a correlation chart to find out the Unconfined Compressive Strength (UCS) of other interval in the formation.