Sand production is one of the more critical issues causing delays and high costs to the petroleum production industry. To measure solid production in the hydrocarbon stream a number of sand monitors have been developed. Such monitors are installed in the flow line and are intended to provide information such as the onset of solid production or the amount of produced solids. Most sand monitors are based on the measurement of erosion due to impingement of sand particles or measuring ultrasonic signals generated by particle impacts on the pipe wall or piezoelectric elements. Having described the principal behind available monitors in the industry, capabilities and limitation of each type is explained in Part 1. Part 2 is comprised of a literature review carried out on the techniques which have the potential to be utilised in new generations of solids monitors. The principles of such methods as well as their advantages and disadvantages for solids monitoring applications are mentioned. In Part 3 subjects such as improving the data quality and data interpretation of current techniques, integration of available techniques into a single piece of equipment, and ranking of the most promising cases which are worthy of further investigation are discussed.

Deep gas reservoirs are going to play more important roles in meeting growing demand of natural gas throughout the world. Due to extreme conditions of downhole stresses, pressure and temperature that occur in deep gas wells, maintaining cement mechanical integrity and zonal isolation have become critical concerns of industry during drilling, completion, and production of such wells. Cement sheath is expected to provide a flawless annular seal between casing and formation along the wellbore. However; cement failure cases which are being reported regularly show that there is still need for understanding extreme downhole conditions and the behavior of cement sheath experiencing such an environment. Although Uniaxial Compressive Strength (UCS) of cement is commonly regarded as the most important mechanical property of cement, recent theoretical and experimental results show that other mechanical properties of cement can be even more determinative in its failure.In this study, Finite Element Method (FEM), a widely-used robust numerical tool, is used for simulation of the downhole environment by modeling temperature, pressures, stresses, downhole materials and their interactions. Using this approach magnitude, direction and type of induced stresses in casing, cement, and formation have been determined. Furthermore; a series of sensitivity analyses was performed to reveal the effects of variation of various parameters such as casing internal pressure, differential horizontal stress and casing eccentricity, on the induced stresses in the cement sheath.Radial, tangential and von Mises stress profiles in the deep gas wells cements were investigated. Furthermore, the effect of casing internal pressure, differential horizontal stress and casing eccentricity were studied in the model. Results show that deep gas wells' cements experience extreme amounts of thermal and mechanical stresses and special consideration is required in cement selection.

Horizontal drilling and hydraulic fracturing are two reliable technologies which have made recovery of tight/shale gas economically viable. A common practice is to drill horizontal well parallel to the minimum horizontal stress, consider short perforation intervals and hydraulically fracture the formation. It is expected that the created fractures would be perpendicular to the horizontal well (transverse fractures). Determining the number of fractures in such horizontal wells is of great interest by the industry. Although one may assume that the more the number of fractures the better the productivity, there is always an optimum number of fractures (hence optimum fracture spacing) which is obtained based on both production rate of the reservoir and its cumulative production. In this paper, different sensitivity analyses on physical optimization parameters are combined by economical evaluation to find the optimum value of fractures spacing (number of fractures), and the length of horizontal section. These optimization analyses have been done on horizontal section length, total permeability, anisotropic permeability ratio, and drainage area. Analyses have been performed based on the values of gas production rates, cumulative production, and defined K value. Finally, economical optimization which was performed using U.S. historical monthly gas prices, inflation and interest rates over a period of 27 years, was coupled with production data obtained from modeling. All the costs and revenues were converted to U.S. Dollar value in 2009. This evaluation shows that for each specific reservoir an optimization study is required and there is no unique solution for all types of reservoirs. However, the gas price forecast is the main factor which governs the whole optimization process.

Several parameters are involved in a hydraulic-fracturingoperation, which is a technique used mainly in tight formations to enhance productivity. Formation properties, state of stresses in the field, injecting fluid characteristics, and pumping rate are among several parameters that can influence the process. Numerical analysis is conventionally run to simulate the hydraulic-fracturing process. Before operating the expensive fracturing job in the field, however, it would be useful to understand the effect of various parameters by conducting physical experiments in the lab. Laboratory experiments are also valuable for validating the numerical simulations. Applying the scaling laws, which are to correspond to the field operation with the test performed in the lab, are necessary to draw valid conclusions from the experiments. Dimensionless parameters are introduced through the scaling laws that are used to scale-down different parameters including the hole size, pump rate and fluid viscosity to that of the lab scale. Sample preparation and following a consistent and correct test procedure in the lab, however, are two other important factors that play a substantial role in obtaining valid results. The focus of this peer-reviewed paper is to address the latter aspect; however, a review of different scaling laws proposed and used will be given.The results presented in this study are the lab tests conducted using a true triaxial stress cell (TTSC), which allows simulation of hydraulic-fracturing under true field stress conditions where three independent stresses are applied to a cubic rock sample.

Hydraulic fracturing is known as one of the most common stimulation techniques performed in oil and gas wells for maximising hydrocarbon production. It is a complex procedure due to numerous influencing factors associated with it. As a result, hydraulic fracturing monitoring techniques are used to determine the real-time extent of the induced fracture and to prevent unwanted events. Although the well-known method of monitoring is the microseismic method, active monitoring of a hydraulic fracture has shown capable of providing useful information about the fracture properties in both laboratory conditions and field operations. In this study, the focus is on laboratory experiment of hydraulic fracturing using a true-triaxial cell capable of simulating field conditions required for hydraulic fracturing. By injecting high-pressure fluid, a hydraulic fracture was induced inside a 20 cm cube of cement. Using a pair of ultrasonic transducers, transmission data were recorded before and during the test. Both cases of an open and closed hydraulic fracture were investigated. Then, using a discrete particle scheme, seismic monitoring of the hydraulic fracture was numerically modelled for a hexagonally packed sample and compared with the lab results. The results show good agreements with data in the literature. As the hydraulic fracture crosses the transducers line, signal dispersion was observed in the compressional wave data. A decrease was observed in both the amplitude and velocity of the waves. This can be used as an indicator of the hydraulic fracture width. As the fracture closes by reducing fluid pressure, a sensible increase occurred in the amplitude of the transmitted waves while the travel time showed no detectable variations. The numerical model produced similar results. As the modelled hydraulic fracture reached the source-receiver line, both amplitude and velocity of the transmitted waves decreased. This provides hope for the future real-time ability to monitor the growth of induced fractures during the fraccing operation. At present, however, it still needs improvements to be calibrated with experimental results.