The significance of exploring deep and ultra-deep wells is increasing rapidly to meet the increased global demands on oil and gas. Drilling at such depth introduces a wide range of difficult challenges and issues. One of the challenges is the negative impact on the drilling fluids rheological properties when exposed to high pressure high temperature (HPHT) conditions and/or becoming contaminated with salts, which are common in deep drilling or in offshore operations.
The drilling engineer must have a good estimate for the values of rheological characteristics of a drilling fluid, such as viscosity, yield point and gel strength, and that is extremely important for a successful drilling operation. In this research work, experiments were conducted on water-based muds with different salinity contents, from ambient conditions up to very elevated pressures and temperatures.
In these experiments, water based drilling fluids containing different types of salt (NaCl and KCl) and at different concentrations were tested by a state-of-the-art high pressure high temperature viscometer. In this paper, the effect of different electrolysis (NaCl and KCl) at elevated pressures (up to 35,000 psi) and elevated temperatures (up to 450 ºF) on the viscosity of water based mud has been presented.
In predicting the geotechnical constraint against pipeline movement usingfinite element methods, the treatment of the pipe/soil interface contactbehavior is of utmost importance, especially in the tangential direction. Thisstudy focuses on the interpretation of soil resistance to axial pipe movementin cohesive soil material for oblique loading, specifically the effect ofchanging the interface shear stress limit and friction coefficient. The mainfinding of the present study is that the incorporation of a shear stress limitin the definition of tangential shear behavior has a considerable effect on theaxial pipeline reaction forces. Without the shear stress limit, the maximumaxial forces due to oblique pipe movement are effectively doubled in comparisonto a limit equal to half of the undrained shear strength. A simple analyticalmethod is provided to estimate the maximum oblique axial soil resistance inundrained conditions. The effect of changing the assumed frictional behavior isalso discussed with respect to predicting the soil reaction forces acting on anice keel during an undrained gouging event in cohesive soil.
Marshall, P.W. (Department of Civil and Environmental Engineering, National University of Singapore) | Sohel, K.M.A. (Department of Civil and Environmental Engineering, National University of Singapore) | Liew, J.Y. Richard (Department of Civil and Environmental Engineering, National University of Singapore) | Jiabao, Yan (Department of Civil and Environmental Engineering, National University of Singapore) | Palmer, A. (Department of Civil and Environmental Engineering, National University of Singapore) | Choo, Y.S. (Department of Civil and Environmental Engineering, National University of Singapore)
There is a wide range of offshore structures which may be constructed byeither steel or concrete materials to be used in the arctic region, such assteel tower platforms, caisson-retained islands, shallow-water gravity-basecaisson, jack-up structures, bottom-founded deep-water structures, floatingstructures, well protectors, seafloor templates and breakwaters. One commonfeature of these structures is that they must be able to resist the highlateral forces from the floating ice and transmit these forces to thefoundation. This study explores the use of Steel-Concrete-Steel (SCS) curvedsandwich system for arctic caisson structures. SCS sandwich system, whichcombines the beneficial effects of steel and concrete materials, has promisingbenefits over conventional plates and stiffeners design and heavily reinforcedconcrete design because of their high strength-to-steel weight ratio and highresistance to contact and impact loads. Shear connectors have been proposed toprovide bonding between the external steel plates and high-performancecementitious core materials. Finite element analyses and large-scale testresults showed that SCS sandwich panels without mechanical bond enhancement arevulnerable to interfacial shear failure and impairment of structural integritywhen subject to shrinkage and thermal strains, accidental loads, and impact.The proposed SCS sandwich system features mass-produced mechanical shearenhancement and/or cross-ties. It can reduce structure complexity, particularlyin the number of weld joints which are prone to fatigue, hence increasingservice life, cutting down the cost of fabrication, and reducing the manpowercost to operate, inspect, and maintain the structure in the long run.Considering local ice load, the punching shear and shell bending strength ofthe SCS sandwich composite shell is studied experimentally. Test results showedthat the SCS sandwich panels, which are designed using the ISO ice load, arecapable of resisting the localized contact and punching loads causedthereby.
This paper was selected for presentation by an ATC program committee following review of information contained in an abstract submitted by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of OTC copyright. Abstract The development of arctic resources requires wells to be drilled, cased, and cemented through permafrost. Permafrost presents unique challenges, especially to cementing operations, requiring a cement system with the capability to perform in the subfreezing permafrost environment. The performance required is that the cement provides isolation, exhibits low heat of hydration, and sets with sufficient strength to provide casing support. There are also specific testing requirements detailed in API recommended practices. In the polar region, there are several approaches used in the design of cement systems. The approaches used in Russia, Canada, and USA (Alaska) are illustrated. The design considerations take into account local conditions and requirements and use knowledge from cementing practices employed in the drilling industry. It is important to understand the current cementing practices in use within the arctic region. The Russian Far East, for example, is almost completely covered in permafrost and holds significant gas reserves that remain largely untapped due to the remoteness of the area and the complexity of drilling through the permafrost layers. Offshore operations are additionally impacted by sea ice, which does not directly affect cementing operations; however, the short operational window certainly requires detailed planning and reliable performance.
Crespo, Freddy E. (University of Oklahoma) | Ahmed, Ramadan Mohammed (University of Oklahoma) | Saasen, Arild (Det norske oljeselskap ASA) | Enfis, Majed (University of Oklahoma) | Amani, Mahmood (Texas A&M University at Qatar)
Surge and swab pressures have been known to cause formation fracture, lost circulation, and well-control problems. Accurate prediction of these pressures is crucially important in estimating the maximum tripping speeds to keep the wellbore pressure within specified limits of the pore and fracture pressures. It also plays a major role in running casings, particularly with narrow annular clearances. Existing surge/swab models are based on Bingham plastic (BP) and power-law (PL) fluid rheology models. However, in most cases, these models cannot adequately describe the flow behavior of drilling fluids. This paper presents a new steady-state model that can account for fluid and formation compressibility and pipe elasticity. For the closed-ended pipe, the model is cast into a simplified model to predict pressure surge in a more convenient way. The steady-state laminar-flow equation is solved for narrow slot geometry to approximate the flow in a concentric annulus with inner-pipe axial movement considering yield-PL (YPL) fluid. The YPL rheology model is usually preferred because it provides a better description of the flow behavior of most drilling fluids. The analytical solution yields accurate predictions, though not in convenient forms. Thus, a numerical scheme has been developed to obtain the solutions. After conducting an extensive parametric study, regression techniques were applied primarily to develop a simplified model (i.e., dimensionless correlation). The performance of the correlation has been tested by use of field and laboratory measurements. Comparisons of the model predictions with the measurements showed a satisfactory agreement. In most cases, the model makes better predictions in terms of closeness to the measurements because of the application of a more realistic rheology model. The correlation and model are useful for slimhole, deepwater, and extended-reach drilling applications.
LWD sonic tools have been used for simple geosteering since their introduction in the 1990s. The measurements typically were limited to the compressional-wave arrivals and (if available) refractedshear-wave velocities. The use of realtime information was limited to simple correlation or direct-interpretation techniques. The practical use of these measurements was limited by the complexity of the measurement in terms of environmental conditions. These tools have found new application and use in recent work in shale-reservoir systems, including the Haynesville, Eagle Ford, Woodford, and Marcellus. In addition to using the compressional-and shear-wave data, these measurements are processed to provide dynamic data for Young's modulus and Poisson's ratio.
High molecular weight partially hydrolyzed polyacrylamides (HPAM), have been shown to effectively increase oil recovery of medium viscous and heavy oil.
Using a rheometer, these polymers show shear thinning behavior. However, determining the apparent viscosity from coreflood tests for different frontal velocities, an increase in the apparent viscosity is observed. This apparent increase is attributed to the visco-elastic properties of the polymers.
In this paper, a set of laboratory experiments has been performed for cores similar to the rock in the 8th Torton Horizon (8 TH) of the Matzen Field in Austria. The results show that for the conditions in the near-wellbore region of the reservoir, an increase in apparent viscosity is expected. In addition, the relationship of velocity versus apparent viscosity for pre-sheared polymers was investigated. Dependent on the amount of pre-shearing, the apparent viscosity was significantly decreased. For different polymer concentrations, the apparent viscosity versus velocity of the pre-sheared polymers was almost identical.
A polymer injection pilot performed in the 8 TH in the Matzen Field in Austria confirmed that shearing of the polymer solution in the near-wellbore occurs for injection below the fracturing pressure. Above the fracturing pressure, the flow velocities are significantly decreased owing to the large surface area of the fracture. Hence, polymer injection should be performed above the fracturing pressure to improve sweep efficiency.
Introduction and motivation
Polymer injection has been shown to be an effective enhanced oil recovery method for hydrocarbon fields containing medium viscous oil. There are two main uncertainties for a polymer injection project, (1) the displacement efficiency (2) injectivity. Both uncertainties are crucial for the performance of a polymer project, the displacement efficiency determines the required amount of polymer per incremental barrel whereas the injectivity effects the time-scale and hence time value of polymer injection projects.
In this paper, results of laboratory experiments concerning the injectivity of polymer solutions are presented. The results are then compared with the injectivity observed in a polymer pilot project in Austria.
The paper is organized as follows: first, the reservoir and its production history are described. Then, the setup of the laboratory experiment is covered, followed by a discussion of the results of the laboratory experiments. Next, the field test results are compared with the experimental results.
Miller, Richard D. (Kansas Geological Survey) | Bailey, Bevin (Kansas Geological Survey) | Peterie, Shelby L. (Kansas Geological Survey) | Ivanov, Julian (Kansas Geological Survey) | Markiewicz, Richard D. (U.S. Bureau of Reclamation)
Many problems associated with correlating reflections between different model data can be minimized by incorporating an extensive series of shot gather analysis with the mode separated CMP stacked section. Minimizing fold and reflection characteristics provided key assistance in correlating lithologies between sections. High fold and a wide range of offsets prove key to increasing the confidence and accuracy of correlations between P-and S-wave reflection sections in the shallow portion of the section. Introduction A reliable measure of seismic properties as a function of depth is important to the comprehensive and accurate appraisal of site response and associated impact on surface and subsurface facilities. As well, Vp/Vs ratios provide key insights into lithology, pore fluid/gas pressure and porosity, material properties, and a variety of engineering characteristics.