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Lost circulation and wellbore failure are common problems in the petroleum industry and they increase drilling costs dramatically. Casing drilling in depleted zones helps reduce drilling costs and problems related to lost circulation and wellbore failure. Thus, casing drilling is an important technology to minimize or eliminate conventional drilling problems in depleted zones. This thesis is focused on a study of smear effect in casing drilling in depleted formations. It is based on information about casing drilling and a commercial computer software ABAQUS. The smearing mechanism of drilling solids into the wellbore wall and the effects of parameters that affect the stress distribution around the wellbore wall are studied. Moreover, multiple wellbore cracks are studied to determine their effects on hoop stress distribution and all the results are given at the results chapter of this study. All the discussions about the changing parameters are given in results section. In conclusion, the smear effect in casing drilling can significantly improve hoop stresses around the wellbore and lost circulation problems can be minimized by using casing as a drilling string. These models can be used as a basic tool to understand smear effects in casing drilling in depleted formations. / text

Casing has a higher risk of failure in a compacting reservoir than in a typical reservoir. Casing fails when reservoir compaction induces compression and shear stresses onto it. They compact as reservoir pressure depletes during production. High compaction reservoirs typically are composed of unconsolidated, overpressured rocks such as chalk, diatomite, and sandstone. Pore pressure depletion increases effective stress, which is the rock matrix stress pushing upward against overburden pressure. Effective stress may exceed rock compressive strength, inducing compaction. Wells in compacting reservoirs risk high failure and deformation rates. This project introduces the concept of structural reliability to quantify casing failure risks in compacting reservoirs. This research developed probabilistic models for casing capacities using current design methods and a reservoir compaction load using finite-element model simulations. Probabilistic models were used in creating two limit-states functions to predict casing failure: axial yielding and buckling failures. A limit-state function describes the casing condition as the casing experiences a reservoir compaction load. The limit state function is the input in component and system analyses for casing fragility and conditional probability of casing failure. Fragilities can predict casing probability of failure as reservoir pressure is depleting. Sensitivity and importance analyses are also performed to determine the importance of parameters affecting the casing reliability. Applying the knowledge produced from this research to casing design methods can improve design reliabilities and forecast the risk of casing failure in compacting reservoirs.

It is widely understood that injection and production activities can induce additional stress fields that will couple with the in situ stress field. An increased shear stress may cause serious casing stability issue, and casing integrity is one of the major issues in the development of an oilfield. In this thesis, I will present a methodology for semi-quantitatively addressing the physical processes, the occurrence, and the key influential factors associated with large-area casing shear issues in Daqing Oilfield. In the research, I will investigate reservoir heterogeneity and the far-field stress field in the Daqing Oilfield, China; I will review fundamental theories of rock strength, rock failure, casing shear, and techniques for coupling fluid flow and mechanical response of the reservoirs; and I will present mathematical simulations of large-area casing shear in one typical area (X1-3B) in Daqing Oilfield, under different regimes of water-affected shale area ratio and block pressure difference. Heterogeneity in Daqing Oilfield varies according to the scale. Mega-heterogeneity is not too serious: the geometry of the oilfield is simple, the structure is flat, and faults are numerous and complex, but distributed evenly. Macro-heterogeneity is, however, intense. Horizontal macro-heterogeneity is associated with lateral variations because of different depositional facies. Vertical macro-heterogeneity of Daqing Oilfield because of layering is typified by up to 100 individual sand layers with thickness ranging from 0.2 to 20 m and permeability ranging from 20 to 1600 mD (average 230 mD). Furthermore, there are a number of stacked sand-silt-shale (clastic lithofacies) sequences. Mercury porosimetry and photo-micro-graphic analyses were used to investigate the micro-heterogeneity of Daqing Oilfield. This method yields a complete pore size distribution, from several nanometers to several thousands of micro-meters as well as cumulative pore volume distributions, pore-throat aspect ratios, and fractal dimensions. The fractal dimension can be used to describe the heterogeneity at the pore scale; for sandstones, the larger the fractal dimension of a specific pore structure, the more heterogeneous it is. Reservoir sandstones of Daqing Oilfield have similar porosity and mineralogy, so their micro-heterogeneity lies in a micro-structure of considerable variability. Differences in micro-structure affect permeability, which also varies considerably and evidences a considerable amount of micro-scale anisotropy. Finally, the number and nature of faults in the oilfield make the macro-scale heterogeneity more complex. Rock strength is affected by both intrinsic factors and external factors. Increased water saturation affects rock strength by decreasing both rock cohesion and rock friction angle. In Daqing Oilfield, is seems that a 5% increase of water content in shale can decrease the maximum shearing resistance of shale by approximately 40%. Hysteretic behavior leads to porosity and permeability decreases during the compaction stage of oilfield development (increasing σ'). Also, injection pressures are inevitably kept as high as possible in the pursuit of greater production rates. These lead to non-homogeneous distributions of pressures as well as in changes of material behavior over time. Loss of shear strength with water content increase, inherent reservoir heterogeneity, and long periods of high-pressure water injection from a number of wells are three key factors leading to casing shear occurring over large areas in Daqing Oilfield. Reservoir heterogeneity and structural complexity foster uneven formation pressure distribution, leading to inter-block pressure differences. Sustained long-term elevated pressures affect overburden shale mechanical strength as well as reducing normal stresses, and the affected area increases with time under high-pressure injection so that the affected areas overlap at the field scale and alter the in situ stress field. Once the maximum compressive stress parallels or nearly parallels the differential pressure, and the water-affected shale area is big enough, the shear stability of the interface between the shale and the sandstone is severely compromised, and when the thrust stress imposed exceeds the shearing resistance, the strata will slip in a direction corresponding to the vector from high-pressure to low-pressure areas. The change in this slip and creep displacement field is the major reason for the serious casing deformation damage in Daqing Oilfield. To quantify the scale effect of the water-affected shale area on casing stability, coupled non-linear poroelastic fluid flow was simulated for a typical area. The Daqing Oilfield simulation result is in coincidence with the in situ observation of disturbed stress fields and casing displacement. The water-affected area has a scale effect on the casing stability. The ratio of the water-affected shale formation area to the total area influences the stability coefficient much more than the block pressure difference. In the studied area, under conditions of injection pressure of 12.7 MPa and no more than 2.5 MPa block pressure difference, the water-affected ratio should be smaller than 0.50 or so in order to maintain areal casing stability. By history matching, in the studied area under current development condition and considering the water-affected ratio, so long as the injection pressure and pressure differential between blocks are controlled to be less than 12.7 MPa and 0.86 MPa respectively, formation shear slip along a horizontal surface will no longer occur.

It is widely understood that injection and production activities can induce additional stress fields that will couple with the in situ stress field. An increased shear stress may cause serious casing stability issue, and casing integrity is one of the major issues in the development of an oilfield. In this thesis, I will present a methodology for semi-quantitatively addressing the physical processes, the occurrence, and the key influential factors associated with large-area casing shear issues in Daqing Oilfield. In the research, I will investigate reservoir heterogeneity and the far-field stress field in the Daqing Oilfield, China; I will review fundamental theories of rock strength, rock failure, casing shear, and techniques for coupling fluid flow and mechanical response of the reservoirs; and I will present mathematical simulations of large-area casing shear in one typical area (X1-3B) in Daqing Oilfield, under different regimes of water-affected shale area ratio and block pressure difference. Heterogeneity in Daqing Oilfield varies according to the scale. Mega-heterogeneity is not too serious: the geometry of the oilfield is simple, the structure is flat, and faults are numerous and complex, but distributed evenly. Macro-heterogeneity is, however, intense. Horizontal macro-heterogeneity is associated with lateral variations because of different depositional facies. Vertical macro-heterogeneity of Daqing Oilfield because of layering is typified by up to 100 individual sand layers with thickness ranging from 0.2 to 20 m and permeability ranging from 20 to 1600 mD (average 230 mD). Furthermore, there are a number of stacked sand-silt-shale (clastic lithofacies) sequences. Mercury porosimetry and photo-micro-graphic analyses were used to investigate the micro-heterogeneity of Daqing Oilfield. This method yields a complete pore size distribution, from several nanometers to several thousands of micro-meters as well as cumulative pore volume distributions, pore-throat aspect ratios, and fractal dimensions. The fractal dimension can be used to describe the heterogeneity at the pore scale; for sandstones, the larger the fractal dimension of a specific pore structure, the more heterogeneous it is. Reservoir sandstones of Daqing Oilfield have similar porosity and mineralogy, so their micro-heterogeneity lies in a micro-structure of considerable variability. Differences in micro-structure affect permeability, which also varies considerably and evidences a considerable amount of micro-scale anisotropy. Finally, the number and nature of faults in the oilfield make the macro-scale heterogeneity more complex. Rock strength is affected by both intrinsic factors and external factors. Increased water saturation affects rock strength by decreasing both rock cohesion and rock friction angle. In Daqing Oilfield, is seems that a 5% increase of water content in shale can decrease the maximum shearing resistance of shale by approximately 40%. Hysteretic behavior leads to porosity and permeability decreases during the compaction stage of oilfield development (increasing σ'). Also, injection pressures are inevitably kept as high as possible in the pursuit of greater production rates. These lead to non-homogeneous distributions of pressures as well as in changes of material behavior over time. Loss of shear strength with water content increase, inherent reservoir heterogeneity, and long periods of high-pressure water injection from a number of wells are three key factors leading to casing shear occurring over large areas in Daqing Oilfield. Reservoir heterogeneity and structural complexity foster uneven formation pressure distribution, leading to inter-block pressure differences. Sustained long-term elevated pressures affect overburden shale mechanical strength as well as reducing normal stresses, and the affected area increases with time under high-pressure injection so that the affected areas overlap at the field scale and alter the in situ stress field. Once the maximum compressive stress parallels or nearly parallels the differential pressure, and the water-affected shale area is big enough, the shear stability of the interface between the shale and the sandstone is severely compromised, and when the thrust stress imposed exceeds the shearing resistance, the strata will slip in a direction corresponding to the vector from high-pressure to low-pressure areas. The change in this slip and creep displacement field is the major reason for the serious casing deformation damage in Daqing Oilfield. To quantify the scale effect of the water-affected shale area on casing stability, coupled non-linear poroelastic fluid flow was simulated for a typical area. The Daqing Oilfield simulation result is in coincidence with the in situ observation of disturbed stress fields and casing displacement. The water-affected area has a scale effect on the casing stability. The ratio of the water-affected shale formation area to the total area influences the stability coefficient much more than the block pressure difference. In the studied area, under conditions of injection pressure of 12.7 MPa and no more than 2.5 MPa block pressure difference, the water-affected ratio should be smaller than 0.50 or so in order to maintain areal casing stability. By history matching, in the studied area under current development condition and considering the water-affected ratio, so long as the injection pressure and pressure differential between blocks are controlled to be less than 12.7 MPa and 0.86 MPa respectively, formation shear slip along a horizontal surface will no longer occur.

Fossil fuels and their byproducts are a vital part of our economy, and society. Until renewable energy sources and energy storage technologies advance to the point where they are reliable and inexpensive, the US Economy will continue to depend upon fossil fuels. Current resources are being consumed, and the "easy to reach" reserves are becoming depleted. This leads to the requirement for more exploratory drilling, and the potential for more disasters like the recent Deepwater Horizon spill in the Gulf of Mexico. Drilling is the first of several steps in the creation of a productive oil or natural gas well. Completing a well involves casing the walls in concrete to prevent damage to the surrounding rock formations and to ensure that all of the oil or gas is captured without escaping to the surrounding environment. Ensuring the piping, which is used to case wells, is assembled correctly and to manufacturer's specifications is the focus of this study. Individual pipe sections are screwed together with a requirement for torque and number of turns. Each joint must be verified to ensure integrity, and minimize the possibility of a spill or leak. The torque measurement can be accomplished by a "torque sub", a sensor installed in-line with the drill string. The torque sub is a wireless sensor that transmits torque data to the control system for logging and display. This thesis defines the parameters required to integrate a "number of turns" measurement into an existing torque sub so that both parameters can be captured, recorded and reported using a single device. The Yost Engineering 3-Space Sensor was evaluated for use in this application. The configuration that gave the most accurate data was selected, along with the determination of some correction factors to account for site specific variation in the signals. A calibration algorithm is discussed, along with several unique methods for ensuring that the sensor output doesn't drift over the course of the joint make-up process. / text

The implementation of a ported shroud casing treatment is often used to extend the operating range of a centrifugal compressor. This work utilizes the STAR-CCM+ CFD package to analyze steady-state, single-passage simulations of a centrifugal compressor with and without a ported shroud to better understand how a ported shroud affects compressor flow physics. Verification and validation of simulations were conducted by comparison of results with a time-accurate full-annulus simulation and experimental data. Four different ported shroud revisions were considered and modeled along the full range of their stable operation, with emphasis placed on the flow limits of choke and stall. A ported shroud is found to improve the choked mass flow limit by increasing the aerodynamic area of the compressor. Near-stall operation is improved through flow recirculation through the ported shroud. This flow, which is induced with a large component of tangential velocity from having passed the impeller blades' leading edge once, reduces the impeller incidence. The influence of a strut is found to restrict both limits of operation by reducing the aerodynamic area and obstruction of tangential velocity. The revisions considered demonstrate that facilitation of flow entering the ported shroud under either near-stall or choked conditions causes a noteworthy improvement in performance. Such alterations, in this application, demonstrate a 3.3% improvement in choked mass flow rate under choked conditions and an 1.3 degree reduction in impeller incidence under near-stall conditions, as compared to the initial ported shroud design. Understanding the effect that a ported shroud casing treatment has on compressor flow physics, especially near its limits of operation, suggests methods for improving centrifugal compressor design to increase its stable operating range.

Increasing surface pressure buildup levels and surface venting flow rates on intermediate wellbore casing strings provided an opportunity to analyze wellbore field data to determine a distribution of leakage path permeability values. The gas leakage source in the leaky wellbore originated at depth, and formation gas/fluid traveled along defects in the cement to accumulate at the surface wellhead. The most likely pathway is the cement interface with casing or formation. Due to uncertainty about the location of the leak, and the different methods that were used for calculating leakage parameter values, a range of leakage path permeability values was produced. Most leakage pathway permeability values were greater than intact cement permeability (few microdarcies). This finding supports the practice of using cement filled annuli to provide a safe protective barrier against leakage and to prevent gas flow to surface. Proper cementing techniques are presented in order to identify possible reasons for cracks to form. It is hypothesized that the higher permeability values are a result of cracks in the cement interface with the casing or formation. These types of defects could also be found in wellbores that are in communication with CO2 sequestration reservoirs. The risk of leakage along such existing wellbores associated with CO2 sequestration projects is quantified by the distribution of leakage path permeability. The gas migration path through existing leaky wellbores is an analog for wellbores that are in contact with migrating CO2 plumes. Cracks in the leaky wellbores provide a highly permeable conduit for CO2 to migrate out of the injection zone to the surface. By quantifying leakage path permeability, proper leakage risk assessment can be further developed. / text

The content of this master thesis is design documentation of department of dermatology of hospital. The main point of the work is dispositional and functional designs of the building in accordance with all applicable standards and regulations for this type of building.

Tato diplomová práce otevírá otázku možnosti zlepšení vlastností kompresoru za pomoci numerické simulace proudění. Hlavním cílem je zvýšení operačního rozsahu na jednom stupni axiálního kompresoru s využitím zařízení pro pasivní kontrolu proudu umístěných ve skříni kompresoru. Prvně bylo prověřeno chování víru ve štěrbině mezi lopatkou a skříní následně celkové charakteristiky původního rotoru. Při snižování hmotnostního průtoku simulace odhalila zvýšený vliv koncového výru na hlavní proud. Navíc byl největší koncový vír v režimu blízkém odtrhávání proudění. Z tohoto důvodu byly pro kontrolu koncového víru navrženy čtyři verze drážkování implementováním sinusové úpravy geometrie. Tři ze čtyř testovaných verzí ukázaly možnost výrazného zvýšení rozsahu stabilního proudění. Nicméně prodlužení operačního rozsahu mělo za následek snížení celkové účinnosti. Na konec této práce jsou navrženy doporučení pro další výzkum.