Browsing by Subject "Horizontal wells"
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Item A physically consistent solution for describing the transient response of hydraulically fractured and horizontal wells(Texas Tech University, 2005-05) Ogunsanya, Oluwasegun Babafemi; Oetama, Teddy; Lea, James F.; Heinze, Lloyd R.Conventional horizontal well transient response models are generally based on the line source approximation of the partially penetrating vertical fracture solution. These models have three major limitations: (i) it is impossible to compute wellbore pressure within the source, (ii) it is difficult to conduct a realistic comparison between horizontal well and vertical fracture transient pressure responses, and (iii) the line source approximation may not be adequate for reservoirs with thin pay zones. This work attempts to overcome these limitations by developing a more flexible analytical solution using the solid bar approximation. A technique that permits the conversion of the pressure response of any horizontal well system into a physically equivalent vertical fracture response is also presented. A new type curve solution is developed for a hydraulically fractured and horizontal well producing from a solid bar source in an infinite-acting. Analysis of computed horizontal wellbore pressures reveals that error ranging from 5 to 20% depending on the value of dimensionless radius (rwD) was introduced by the line source assumption. The proposed analytical solution reduces to the existing fully/partially penetrating vertical fracture solution developed by Raghavan et al. as the aspect ratio aspect ratio (m) approached zero (m < 10-4), and to the horizontal fracture solution developed by Gringarten and Ramey as m approaches unity. Our horizontal fracture solution yields superior early time (tDxf < 10-3) solution and improved computational efficiency compared to the Gringarten and Ramey's solution, and yields excellent agreement for tDxf < 10-3. A dimensionless rate function (Beta-function) is introduced to convert the pressure response of a horizontal well into an equivalent vertical fracture response. A step-wise algorithm for the computation of Beta -function is developed. This provides an easier way of representing horizontal wells in numerical reservoir simulation without the rigor of employing complex formulations for the computation of effective well block radius.Item A physically sonsistent solution for describing the transient response of hydraulically fractured and horizontal wells(2005-05) Ogunsanya, Oluwasegun Babafemi; Oetama, Teddy; Lea, James F.; Heinze, Lloyd R.Conventional horizontal well transient response models are generally based on the line source approximation of the partially penetrating vertical fracture solution. These models have three major limitations: (i) it is impossible to compute wellbore pressure within the source, (ii) it is difficult to conduct a realistic comparison between horizontal well and vertical fracture transient pressure responses, and (iii) the line source approximation may not be adequate for reservoirs with thin pay zones. This work attempts to overcome these limitations by developing a more flexible analytical solution using the solid bar approximation. A technique that permits the conversion of the pressure response of any horizontal well system into a physically equivalent vertical fracture response is also presented. A new type curve solution is developed for a hydraulically fractured and horizontal well producing from a solid bar source in an infinite-acting. Analysis of computed horizontal wellbore pressures reveals that error ranging from 5 to 20% depending on the value of dimensionless radius (rwD) was introduced by the line source assumption. The proposed analytical solution reduces to the existing fully/partially penetrating vertical fracture solution developed by Raghavan et al. as the aspect ratio aspect ratio (m) approached zero (m < 10-4), and to the horizontal fracture solution developed by Gringarten and Ramey as m approaches unity. Our horizontal fracture solution yields superior early time (tDxf < 10-3) solution and improved computational efficiency compared to the Gringarten and Ramey's solution, and yields excellent agreement for tDxf < 10-3. A dimensionless rate function (Beta-function) is introduced to convert the pressure response of a horizontal well into an equivalent vertical fracture response. A step-wise algorithm for the computation of Beta -function is developed. This provides an easier way of representing horizontal wells in numerical reservoir simulation without the rigor of employing complex formulations for the computation of effective well block radius.Item Combustion Assisted Gravity Drainage (CAGD): An In-Situ Combustion Method to Recover Heavy Oil and Bitumen from Geologic Formations using a Horizontal Injector/Producer Pair(2012-11-21) Rahnema, HamidCombustion assisted gravity drainage (CAGD) is an integrated horizontal well air injection process for recovery and upgrading of heavy oil and bitumen from tar sands. Short-distance air injection and direct mobilized oil production are the main features of this process that lead to stable sweep and high oil recovery. These characteristics identify the CAGD process as a high-potential oil recovery method either in primary production or as a follow-up process in reservoirs that have been partially depleted. The CAGD process combines the advantages of both gravity drainage and conventional in-situ combustion (ISC). A combustion chamber develops in a wide area in the reservoir around the horizontal injector and consists of flue gases, injected air, and mobilized oil. Gravity drainage is the main mechanism for mobilized oil production and extraction of flue gases from the reservoir. A 3D laboratory cell with dimensions of 0.62 m, 0.41 m, and 0.15 m was designed and constructed to study the CAGD process. The combustion cell was fitted with 48 thermocouples. A horizontal producer was placed near the base of the model and a parallel horizontal injector in the upper part at a distance of 0.13 m. Peace River heavy oil and Athabasca bitumen were used in these experiments. Experimental results showed that oil displacement occurs mainly by gravity drainage. Vigorous oxidation reactions were observed at the early stages near the heel of the injection well, where peak temperatures of about 550?C to 690?C were recorded. Produced oil from CAGD was upgraded by 6 and 2?API for Peace River heavy oil and Athabasca bitumen respectively. Steady O2 consumption for both oil samples confirmed the stability of the process. Experimental data showed that the distance between horizontal injection and production wells is very critical. Close vertical spacing has negative effect on the process as coke deposits plug the production well and stop the process prematurely. CAGD was also laboratory tested as a follow-up process. For this reason, air was injected through dual parallel wells in a mature steam chamber. Laboratory results showed that the process can effectively create self-sustained combustion front in the previously steam-operated porous media. A maximum temperature of 617?C was recorded, with cumulative oil recovery of 12% of original oil in place (OOIP). Post-experiment sand pack analysis indicated that in addition to sweeping the residual oil in the steam chamber, the combustion process created a hard coke shell around the boundaries. This hard shell isolated the steam chamber from the surrounding porous media and reduced the steam leakage. A thermal simulator was used for history matching the laboratory data while capturing the main production mechanisms. Numerical analysis showed very good agreement between predicted and experimental results in terms of fluid production rate, combustion temperature and produced gas composition. The validated simulation model was used to compare the performance of the CAGD process to other practiced thermal recovery methods like steam assistance gravity drainage (SAGD) and toe to heel air injection (THAI). Laboratory results showed that CAGD has the lowest cumulative energy-to-oil ratio while its oil production rate is comparable to SAGD.Item Gas injection techniques for condensate recovery and remediation of liquid banking in gas-condensate reservoirs(2011-05) Hwang, Jongsoo; Sharma, Mukul M.; Sharma, Mukul M.; Mohanty, Kishore K.In gas-condensate reservoirs, gas productivity declines due to the increasing accumulation of liquids in the near wellbore region as the bottom-hole pressure declines below the dew point pressure. This phenomenon occurs even in reservoirs containing lean gas-condensate fluid. Various methods were addressed to remediate the productivity decline, for example, fracturing, gas injection, solvent injection and chemical treatment. Among them, gas injection techniques have been used as options to prevent retrograde condensation by vaporizing condensate and/or by enhancing condensate recovery in gas-condensate reservoirs. It is of utmost importance that the behavior of liquid accumulation near the wellbore should be described properly as that provides a better understanding of the productivity decline due to the originated from impaired relative mobility of gas. In this research, several gas injection techniques were assessed by using compositional simulators. The feasibility of different methods such as periodic hot gas injection and gas reinjection using horizontal wells were assessed using different reservoir fluid and injection conditions. It is shown that both the temperature and composition of the injection fluids play a key role in the remediation of productivity and condensate recovery. The combined effect of these parameters were investigated and the resulting impact on gas and condensate production was calculated by numerical simulations in this study. Design parameters pertaining to field development and operations including well configuration and injection/production scheme were also investigated in this study along with the above parameters. Based on the results, guidelines on design issues relating gas injection parameters were suggested. The various simulation cases with different parameters helped with gaining insight into the strategy of gas injection techniques to remediate the gas productivity and condensate recovery.Item Pressure transient testing and productivity analysis for horizontal wells(Texas A&M University, 2004-11-15) Cheng, YuemingThis work studied the productivity evaluation and well test analysis of horizontal wells. The major components of this work consist of a 3D coupled reservoir/wellbore model, a productivity evaluation, a deconvolution technique, and a nonlinear regression technique improving horizontal well test interpretation. A 3D coupled reservoir/wellbore model was developed using the boundary element method for realistic description of the performance behavior of horizontal wells. The model is able to flexibly handle multiple types of inner and outer boundary conditions, and can accurately simulate transient tests and long-term production of horizontal wells. Thus, it can serve as a powerful tool in productivity evaluation and analysis of well tests for horizontal wells. Uncertainty of productivity prediction was preliminarily explored. It was demonstrated that the productivity estimates can be distributed in a broad range because of the uncertainties of reservoir/well parameters. A new deconvolution method based on a fast-Fourier-transform algorithm is presented. This new technique can denoise "noisy" pressure and rate data, and can deconvolve pressure drawdown and buildup test data distorted by wellbore storage. For cases with no rate measurements, a "blind" deconvolution method was developed to restore the pressure response free of wellbore storage distortion, and to detect the afterflow/unloading rate function using Fourier analysis of the observed pressure data. This new deconvolution method can unveil the early time behavior of a reservoir system masked by variable-wellbore-storage distortion, and thus provides a powerful tool to improve pressure transient test interpretation. The applicability of the method is demonstrated with a variety of synthetic and actual field cases for both oil and gas wells. A practical nonlinear regression technique for analysis of horizontal well testing is presented. This technique can provide accurate and reliable estimation of well-reservoir parameters if the downhole flow rate data are available. In the situation without flow rate measurement, reasonably reliable parameter estimation can be achieved by using the detected flow rate from blind deconvolution. It has the advantages of eliminating the need for estimation of the wellbore storage coefficient and providing reasonable estimates of effective wellbore length. This technique provides a practical tool for enhancement of horizontal well test interpretation, and its practical significance is illustrated by synthetic and actual field cases.