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With an increasing demand for hydrocarbon reservoir produces such as oil, etc., and difficulties in finding green oil fields, the use of Enhanced Oil Recovery (EOR) methods such as polymer, Smart water, and solvent flooding for further development of existing fields can not be overemphasized. For reservoir profitability and reduced environmental impact, it is crucial to consider appropriate well control settings of EOR methods for given reservoir characterization. Moreover, finding appropriate well settings requires solving a constrained optimization problem with suitable numerical solution methods. Conventionally, the solution method requires many iterations involving several computationally demanding function evaluations before convergence to the appropriate near optimum. The major subject of this thesis is to develop an efficient and accurate solution method for constrained optimization problems associated with EOR methods for their value quantifications and ranking in the face of reservoir uncertainties. The first contribution of the thesis develops a solution method based on the inexact line search method (with Ensemble Based Optimization (EnOpt) for approximate gradient computation) for robust constrained optimization problems associated with polymer, Smart water, and solvent flooding. Here, the objective function is the expectation of the Net Present Value (NPV) function over given geological realizations. For a given set of well settings, the NPV function is defined based on the EOR simulation model, which follows from an appropriate extension of the black-oil model. The developed solution method is used to find the economic benefits and also the ranking of EOR methods for different oil reservoirs developed to mimic North Sea reservoirs. Performing the entire optimization routine in a transformed domain along with truncations has been a common practice for handling simple linear constraints in reservoir optimization. Aside from the fact that this method has a negative impact on the quality of gradient computation, it is complicated to use for non-linear constraints. The second contribution of this thesis proposes a technique based on the exterior penalty method for handling general linear and non-linear constraints in reservoir optimization problems to improve gradient computation quality by the EnOpt method for efficient and improved optimization algorithm. Because of the computationally expensive NPV function due to the costly reservoir simulation of EOR methods, the solution method for the underlying EOR optimization problem becomes inefficient, especially for large reservoir problems. To speedup the overall computation of the solution method, this thesis introduces a novel full order model (FOM)-based certified adaptive machine learning optimization procedures to locally approximate the expensive NPV function. A supervised feedforward deep neural network (DNN) algorithm is employed to locally create surrogate model. In the FOM-based optimization algorithm of this study, several FOM NPV function evaluations are required by the EnOpt method to approximate the gradient function at each (outer) iteration until convergence. To limit the number FOM-based evaluations, we consider building surrogate models locally to replace the FOM based NPV function at each outer iteration and proceed with an inner optimization routine until convergence. We adapt the surrogate model using some FOM-based criterion where necessary until convergence. The demonstration of methodology for polymer optimization problem on a benchmark model results in an improved optimum and found to be more efficient compared to using the full order model optimization procedures.

Master's thesis in Petroleum engineering In this experimental study, unsupported pipe experiments are conducted. Information regarding intervention operation, focusing on snubbing operations in live well interventions and unsupported buckling during these operations, are described as well as the conducted experiments. The loads and forces acting on the pipes during these experiments are compared to the already known theoretical buckling load calculations. Determination of buckling loads, yield strength and Young’s elasticity modulus has been conducted on short to intermediate columns for local buckling in this study. Equations used in the oil and gas industry today are used to show the experimental results, such as slenderness ratio, short column and intermediate column critical buckling loads. At last, the use of the two different slenderness ratio equations are investigated and compared with the experiment results. Indication from these results shows that the use of one of these two slenderness ratio equations, used in the oil and gas industry today, may not be applicable after all.

Master's thesis in Petroleum engineering Design and planning in drilling a well are a key for successful before to execute drilling operation. A good understanding of wellbore stability, design mud, casing, cementing, BHA & drillstring, drilling bit, hole cleaning & hydraulic are an important process in well planning. Good design and planning can keep drilling activity on track based on schedule and it can avoid non-productive time during drilling. By knowing the rock mechanics properties is important in the drilling design. Many problems happen during drilling relate to rock mechanics. One of the problem during drilling relates to rock mechanics is wellbore instability. Before drilling, rock in equilibrium condition but after drilling, there is a disturbance in the rock formation and it changes stress distribution. Knowing the insitu stresses (vertical stress, maximum horizontal stress, minimum horizontal stress) and stresses around the borehole wall (radial stress, axial stress and tangential stress) are important. With knowing these parameters, wellbore collapse caused by shear stress can be avoided. In this thesis will analyze the sensitivity of the failure criteria with respect to horizontal stress anisotropy and depth, in order to evaluate which failure criteria to recommend under which stress conditions. Mohr-Coulomb, Modified Lade and Stassi d' Alia models will be used to figure out the failure criteria. The result of these models is used to estimate critical mud weight to prevent wellbore collapse. This study also will analyze drilling optimization through casing design, hole cleaning and hydraulic design, drillstring and bottom hole assembly (BHA) design. Landmark drilling software is used to design drilling optimization. With a good well design, it is expected that it can manage drilling on the track based on budget and it can mitigate problems during drilling. Keywords: Pore pressure, fracture pressure, insitu stress, rock mechanics, collapse pressure formation, casing design, cutting transport & hydraulic methods

Master's thesis in Petroleum engineering Production of oil on the Norwegian continental shelf started in the early 70’s. Many of these fields are now reaching the end of their production time. The industry is now awaiting a “plug wave” in the not too distant future. Decommission is a time-consuming procedure, and the cost of P&A can end up being 25 % of the total cost of the well. The task given from Wintershall was to plan P&A operation by setting a dual barrier plug against the creeping clay in the Hordaland formation. The Hordaland green clay will creep in and seal around the casing and create a bonding with the casing. This method has saved operators on the Norwegian continental shelf for millions of NOK, by avoiding milling or squeeze cement job. All the wells at Brage require permanent P&A in order to control subsurface pressure and prevent the free flow of pore fluids to the seabed. The wells at Brage was categorized depending on the different casing design. The objective was to determine the time for P&A for every category. There were three different casing designs that stood out: pre-drilled wells, production liner with tie-back casing and simplified casing design. The most likely time for plugging the 40 wells at Brage is estimated to be around 3 years. The time estimate is done with the technology available today. In the future there might be new technology that will enable the operator to P&A the field in a more cost-effective way. Many service companies are working on developing tomorrows P&A solution. Some of the new technologies will be presented and discussed in this thesis, together with the use of formation as a barrier.

Master's thesis in Petroleum engineering Magnetic distortion of magnetometer readings affects the accuracy and efficiency of the wellbore positioning operations, which in turn degrades the industrial viability of the magnetic measurements while drilling survey instrument. Magnetic disturbances to the geomagnetic field reduces the wellbore positional accuracy and leads to uncertainties in the decision- making process. This master project provides an overview of the industrial limitations of magnetometers, highlights and maps the magnetic elements that affect the sensor readings. This leads to additional difficulties and uncertainties in the decision- making process, which is included. The robustness and industrial capabilities of the interpolation in- field referencing method has been validated through presentation of case studies, mapping of its features and applications, comparison with other geomagnetic referencing techniques and analysis. This work concludes that the interpolation in- field referencing technique increases the accuracy of wellbore positioning and improves decision- making during drilling operations. However, limitations and shortfalls of the interpolation in- field referencing method were also recognized. These need to be addressed and corrected in order to reaffirm the industrial use of this survey method over competitive survey systems.

Master's thesis in Petroleum engineering Cementing wells with severe temperatures and/or pressures has become a common matter over the years. Running casing and designing the cement job is very difficult with temperatures above 150°C (300°F) which is a common temperature range in geothermal steam- and HPHT wells. The downhole temperature controls the pace of cement hydration and one major concern in geothermal- and HPHT wells is maintaining strength stability in cementing compositions at 370°C (700°F). Cementing thermal wells requires solutions for obstacles, such as increased thickening time, strength retrogression, thermal shock, lost circulation and corrosion. These obstacles requires for a complex job design, not only in, a chemical properties design view, but also in placement technique and pumping pace of the slurry. Comprehensive research to enhance the integrity of the cement in thermal environments has been done, and previous work failures has contributed to several finding that has improved the cementing solutions for geothermal well conditions, especially the ones containing corrosive formation fluids. Three cases have been studied, together with a literature review to provide an overview of the cement job designs chosen, integrity of the cement slurry, and reasons for failure. Furthermore, the cementing solutions were studied to look at what additives improved integrity and stability. What kind of laboratory tests were performed to support the design solutions. The study has shown that certain cement additives are here to stay, such as silica flour, pozzolans, and elastic-behaving chemicals. A key issue in successful cement sheath integrity has proven to be directly related to proper hole preparations and drilling fluid removal. Knowing as much as possible about the wellbore parameters is necessary to provide proper computer software simulation testing of the cement slurry. Laboratory tests and simulations should be as real as possible, and as many as possible of these tests should be performed to to ensure the cement slurry can withstand the actual well conditions.

Master's thesis in Petroleum engineering Rate of penetration (ROP) is dependent on several factors and it is essential to properly manage and control this in order to save cost of drilling operations. Drillbotics test skid is an automated machine that is expected to drill as vertically as possible into a rock formation of varying compositions. This thesis demonstrates the design approach to controlling ROP by managing the effects of circulation system, WOB, RPM, bit torque and the reaction time of the controller in order to achieve an optimal drilling operation. Also covered are the detailed steps based on the design guidelines for the drillbotics 2016 competition. The results obtained during testing indicated high potential of controlling ROP automatically during drilling operations. The second part of the thesis focused on multiple regression techniques which were used in predicting the ROP of a well by using the coefficients obtained from a near-by well on the same block. The analysis was based on four wells, a pair on two blocks respectively. The technique considered the combined effects of drilling parameters, MSE and D-exponent independently in order to predict the ROP of the nearby well. The results displayed both, the actual ROP and the modelled ROP plots for comparison.