Oil production decline and excessive water production are prevalent in mature fields and unconventional plays, which significantly impact the profitability of the wells and result in costly water treatment and disposal. To seek for a sustainable development of those wells, reducing the operation cost and extending their economic lives, this paper presents a method of synergistic production of hydrocarbon and electricity, which could harvest the unexploited geothermal energy from the produced water and transfer heat to electricity in the wellbore. Such method is cost-effective, since it does not require any surface power plant facility, and it is replicable in numerous wells including both vertical wells and horizontal wells. By simultaneous coproduction of oil and electricity, the value of existing assets could be fully developed, operation cost could be offset, and the economic life of the well could be extended.
This recently proposed method incorporated thermoelectric power generation technology and oil production. In this method, electricity could be produced by thermoelectric generator (TEG) mounted outside of the tubing wall under temperature gradient created by produced fluid and injected fluids. The aim of this paper is to illustrate the economic practicability of oil-electricity coproduction by using thermoelectric technology in oil wells based on previously proposed design. We examined the technical data of high water-cut oil wells in North Dakota and collected required information with respect to performance thermoelectric power generations. Special emphasis was placed on the key parameters related to project economics, such as thermoelectric material, length of TEG and injection rate. Sensitive studies were carried out to characterize the impact of the key parameters on project profits. We showed that by simultaneously production of oil and electricity, $234,480 of additional value could be generated without interfering with oil production.
The proposed method capitalizes on the unexploited value of produced water and generates additional benefits. This study could provide a workflow for oil and gas operators to evaluate an oil-electricity coproduction project and could act as a guidance to perform and commercialize such project to balance parts of the operation cost and extend the life of the existing assets.
Yoneda, Jun (National Institute of Advanced Industrial Science and Technology) | Takiguchi, Akira (West Japan Engineering Consultants) | Ishibashi, Toshimasa (West Japan Engineering Consultants) | Yasui, Aya (West Japan Engineering Consultants) | Mori, Jiro (West Japan Engineering Consultants) | Kakumoto, Masayo (National Institute of Advanced Industrial Science and Technology) | Aoki, Kazuo (National Institute of Advanced Industrial Science and Technology) | Tenma, Norio (National Institute of Advanced Industrial Science and Technology)
During gas production from offshore gas-HBS, there are concerns regarding the settlement of the seabed and the possibility that frictional stress will develop along the production casing. This frictional stress is caused by a change in the effective stress induced by water movement caused by depressurization and dissociation of hydrate as well as gas generation and thermal changes, all of which are interconnected. The authors have developed a multiphase-coupled simulator by use of a finite-element method named COTHMA. Stresses and deformation caused by gas-hydrate production near the production well and deep seabed were predicted using a multiphase simulator coupled with geomechanics for the offshore gas-hydrate-production test in the eastern Nankai Trough. Distributions of hydrate saturation, gas saturation, water pressure, gas pressure, temperature, and stresses were predicted by the simulator. As a result, the dissociation of gas hydrate was predicted within a range of approximately 10 m, but mechanical deformation occurred in a much wider area. The stress localization initially occurred in a sand layer with low hydrate saturation, and compression behavior appeared. Tensile stress was generated in and around the casing shoe as it was pulled vertically downward caused by compaction of the formation. As a result, the possibility of extensive failure of the gravel pack of the well completion was demonstrated. In addition, in a specific layer, where a pressure reduction progressed in the production interval, the compressive force related to frictional stress from the formation increased, and the gravel layer became thin. Settlement of the seafloor caused by depressurization for 6 days was within a few centimeters and an approximate 30 cm for 1 year of continued production.
Mulyani, Sri (Schlumberger) | Sarmiento, Zammy (KS Orka) | Chandra, Vicky (Sorik Marapi Geothermal Power) | Hendry, Ridha (Sorik Marapi Geothermal Power) | Nasution, Syukri (Sorik Marapi Geothermal Power) | Hidayat, Ryan (Sorik Marapi Geothermal Power) | Jhonny, Jhonny (Schlumberger) | Sari, Pebrina (Schlumberger) | Juandi, Dedi (Schlumberger)
Understanding the reservoir conditions through 3D subsurface modeling is the key to optimize the exploration stage in geothermal field. A calibrated reservoir model based on updated data can be very important for this process. The main challenge of reservoir characterization in a geothermal field is the lack of subsurface data, therefore surface data are useful for reservoir modeling. This study utilized Sorik Marapi geothermal field data as a reference for reservoir modeling. This field is one of the geothermal fields in Indonesia that has been recently drilled, with results indicating the existence of a high temperature-neutral acidity resource. Initial reservoir model has been built from the previous study to create conceptual 3D subsurface model which includes structural, lithology, resistivity, and temperature distribution from surface exploration data, including surface mapping, remote sensing image interpretation, the magnetotelluric method, and subsurface data from six wells data.
The objective of this paper is to calibrate the initial reservoir model with information from an additional ten new wells data to improve delineation for updated reservoir area in the field. Software that allowed multidisciplinary data integration from surface to subsurface information was used for the calibration of the initial 3D model. The workflow to calibrate the model started with data loading and quality control, preparing the old 3D model and comparing it to new well data, analyzing the comparison, and updating the 3D model. Finally, the new delineation of reservoir zone can be determined.
The result of this study is an updated 3D subsurface static model defining the vertical and lateral reservoir boundaries, as well as the prime resource areas, which would be the basis for designing future well targets, and parameters for a dynamic reservoir model. The same model can be expanded to construct the numerical model to match the natural state condition of the field and make forecasts of the future reservoir behavior at different operating conditions. The main properties of the updated 3D model are lithology and temperature, which are important in geothermal reservoir delineation.
Deng, Song (Changzhou University) | Liu, Yali (Changzhou University) | Wei, Xia (No. 2 Gas Production Plant, Changqing Oilfield Company, PetroChina) | Tao, Lei (Changzhou University) | He, Yanfeng (Changzhou University)
Phase change, a major factor that restricts the development of gas hydrate, is likely to cause blockage in well completion section (sieve section - wellbore lifting section), thus resulting in the engineering losses. In view of the defects in the previous studies on the confluence mechanism of completion section of gas hydrate pressure drop method mining under openhole completion technology, the flow of gas hydrate in the well completion section was simplified as the Main-Branch pipe confluence model in this paper. Firstly, a physical model was established. On the basis of the energy conservation law and the Peng-Robinson equation, the temperature and pressure coupling model was also derived. Then, the Fluent software was used to simulate the temperature gradient and pressure gradient changes in the Main-Branch model. The gas hydrate phase diagram and PT environment under different velocity were obtained. Finally, the contrast analysis between theoretical model and numerical simulation was carried out and the established model was verified. Through the study of this paper, it is possible to prevent blockage of the well completion section by means of depressurization, which can provide theoretical guidance for the control of pressure drop when gas hydrate is extracted by depressurization. It is important for the exploitation and continuous production of gas hydrate in the later stage.
Oil and gas exploration in the deep-water areas have become a global hot spot. The deep-water area of the Baiyun sag in the Pearl River Mouth Basin is an important exploration target. The area is a typical deep-water hot basin of a wide range of geothermal gradients. Data from a single borehole shows a geothermal gradient from 4.0 to 6.64°C/100m. High geothermal field has an important control on the reservoir diagenesis, pore evolution and porosity-permeability trends. We analyzed sandstone samples from the ZhuJiang and ZhuHai Group, which were buried in the depth range between 500- and 4000m, and display similar composition and textures. The samples can provide insights into the evolution of reservoir diagenetic features under progressive burial process. We also analyzed sandstone samples frome EnPing Group. In general, the petrological composition was the main controlling factor of reservoir quality. The high geothermal field led to a rapid decrease in the porosity and permeability of deeply buried sandstones. Howerver, the EnPing Group, which has a deeper burial depth, shows good reservoir quality. Compared with the ZhuJiang Group and the ZhuHai Group sandstone, the EnPing Group sandstone is dominantly coarse sandstone with more quartz grains, minor feldspars and rock fragments. The EnPing Group is dominated by primary pores, which has a better porosity-permeability relationship than other groups. The deep-water of the Baiyun sag still has potential for exploration. In particular, EnPing Group sandstone reservoir may become a desirable goal in deep and ultra-deep exploration.
Santoso, Ryan (Physical Science and Engineering Division, King Abdullah University of Science and Technology) | Hoteit, Hussein (Physical Science and Engineering Division, King Abdullah University of Science and Technology) | Vahrenkamp, Volker (Physical Science and Engineering Division, King Abdullah University of Science and Technology)
The tectonic setting of Saudi Arabia enriches the country with significant geothermal resources, such as those in Al-Lith and Jizan in the southwestern area. Recently, there has been interest to explore the geothermal potential to diversify the country's energy-mix, which is driven by the Kingdom's Vision 2030. One key challenge in geothermal systems is in their low efficiency compared to traditional hydrocarbon-fired plants. This inefficiency is related to the thermal flow behavior in the subsurface and to the energy conversion technology at the surface. In this study, we provide a workflow for feasibility assessment of geothermal reservoir development with potential application in Saudi Arabia.
The proposed workflow is within the Design of Experiment (DoE) framework, which allows conducting numerous simulations with low computational cost. Computations are performed using a proxy modeling approach, which reflects a multidimensional response-surface emerging from the optimization problem. Two steps in the workflow were found to be critical. First, identify and select the most significant uncertainty parameters to focus the design. Second, address the nonlinearity of the problem by filling up any potential gaps within the response space. In this work, two-level folded Plackett-Burman design is used to identify and select the most significant parameters relative to the energy recovery and enthalpy production factors. Three-level Taguchi design is then applied to create a more rigorous proxy model. We used a space-filling technique to address lack of sampling and nonlinearity in the response surface. Monte Carlo simulations are performed, at the final stage, to generate probabilistic forecasts under uncertainties.
The energy recovery factor and the enthalpy production behavior are found to be influenced by the volume of the reservoir, rock permeability and porosity, heterogeneity, well spacing, and fluid production rate. Our Monte Carlo simulations show that, at the Jizan's geothermal conditions, the energy recovery factor is within 12% to 24%, which is encouraging as they are above the typical recovery factor of 10%-17% worldwide.
Morita, Hiromitsu (National Institute of Advanced Industrial Science and Technology (AIST)) | Muraoka, Michihiro (National Institute of Advanced Industrial Science and Technology (AIST)) | Yamamoto, Yoshitaka (National Institute of Advanced Industrial Science and Technology (AIST))
This paper measures the thermophysical properties of natural methane hydrate (MH)-bearing sediments recovered from the Nankai Trough, Japan. The thermal conductivity, thermal diffusivity, and specific heat of the sample under vertical stress (VS) loading were measured by the hot-disk transient method. The thermal conductivity of the sediments increased with increasing VS. The specific heat and thermal diffusivity have a constant value independent of VS. After MH dissociation, the thermal conductivity and the specific heat dropped significantly, and the thermal diffusivity was increased. In addition, the thermal conductivity, specific heat, and thermal diffusivity were calculated by an estimation model.
Methane hydrate (MH) is expected to be developed as an unconventional natural gas source, replacing existing fossil fuels. MH is a crystalline solid in which cages of hydrogen-bonded water molecules enclose the methane gas molecules. MH is stable in a high-pressure/low-temperature environment. A large amount of MH is known to exist in permafrost on land and in sedimentary layers beneath the seabed (Sloan and Koh, 2007).
The collected seismic data for oil and gas exploration show a wide distribution of bottom-simulating reflections (BSRs) under the seafloor in the Nankai Trough region near the Japan Sea coast. BSRs indicate the lower limit of gas hydrate stability zone in a vertical profile. In 1999, the first Nankai Trough methane hydrate exploration well was drilled. In early 2004, the Japan Ministry of Economy, Trade, and Industry drilled a multiwell from Tokaioki to Kumano-nada (Tsuji et al., 2009). The core was recovered using a pressure-temperature core sampler, which maintained the in-situ condition of 16 excavation sites at water depths ranging from 720 to 2,030 m in the same year. Recovered core analysis confirmed that the MH-bearing sediments in the Nankai Trough area are pore-filling-type hydrates (Fujii, Nakamizu, et al., 2009; Fujii, Saeki, et al., 2009).
At present, along with conventional energy sources continually consumed, renewable energy sources are increasingly favored, especially the clean and inexhaustible geothermal resources have been universally valued both at home and abroad. In particular, the Enhanced Geothermal Systems (EGS), which is mainly aimed to exploit the thermal energy of Hot Dry Rock (HDR) at depths of 3 to 10 kilometers underground, has been full of interest to many countries. However, so far there hasn't been an EGS being successfully put into commercial operation because of its shortcomings such as small scale, low efficiency, etc. In this article, in response to the bottleneck of the study on the development of traditional EGS based on drilling technology (EGS-D), a conceptual model of EGS based upon excavation technology (EGS-E) is innovatively proposed and its main components of underground structure are described in this paper. As for ‘High ground stress, High ground temperature and High osmotic pressure’ initial conditions with regards to deep rock mass, the excavation experience, which is worth being learnt from extensive review of previous study as well as practical experience such as the successful excavation of ultra-deep mines in the gold field of South Africa, is summed up. The underground spatial structure that may be reasonable to the so-called EGS-E is being tried establishing. It is expected to provide with a basis for our subsequent numerical modeling.
Currently, seeking and developing clean new energy is the basic energy exploitation strategy, and the clean and inexhaustible geothermal resources have been universally valued both at home and abroad. Geothermal energy is the heat energy mainly generated by the transmutation of radioactive elements in rocks, which is 2.0934×1018 kJ annually. And the geothermal energy stored at depths of less than 10 kilometers underground was estimated to be 170 million times the amount of heat released from all the coals stored in the earth by Pollack and Chapman in 1977 (Wang Ruifeng, 2002). It can be seen that the reserves of geothermal energy are very considerable.
In spite of its advantages of stability, continuity and high utilization coefficient, the scale of the geothermal energy with temperature less than 150 °C at depths of less than 3 kilometers underground is usually too small to maintain the demand for long-term stable electricity production which is mainly hydrothermal and only accounts for 10% of all the geothermal energy stored in the earth (Guo Jian et al., 2014). Therefore, the enhanced geothermal system (EGS) which aims at exploiting the geothermal energy from hot dry rock (HDR) at depths of 3 to 10 kilometers has gradually attracted people's attention.
The geothermal energy extraction using the fracture-type reservoir in deep crust more than 350-400 °C is suggested. When using the fracture-type reservoir, there is a possibility of aseismic slip rather than seismic slip. However, characteristic and influence on permeability of the aseismic slip is unknown. Therefore, in this study, to clarify the occurrence condition, characteristics and influence on permeability of aseismic slip, injection-induced slip experiment using cylindrical specimen with a 45° tilted tensile fracture was conducted under the condition 200-500 °C. As a result, the followings were clarified. 1) there was a difference in characteristics between the slip start and the subsequent slip, 2) the slip velocity at the beginning of slip was affected by the surface shape of the fracture, 3) and the slip velocity of the subsequent steady slip tended to decrease as the temperature increased. Under 350-500 °C, the pore pressure at the beginning of slip decreased as temperature increased. Therefore, it is suggested that slower slip with a smaller pore pressure, namely, a more stable slip, may occur as the temperature increases. The permeability change before and after the slip experiment was increased at 200, 250 and 300 °C, didn’t change at 350 °C and decreased by half at 500 °C. But since it is not a large decrease of more than one order, it is considered that a sufficient permeability can be maintained in the real geothermal reservoir.
New concept of engineered geothermal development where reservoirs are created in ductile basement is proposed (Asanuma et al., 2012). This potentially has a number of advantages. Suppression of felt earthquakes from/around the reservoirs is one of them (Muraoka et al., 2013). When using this type reservoir, there is a possibility of aseismic slip rather than seismic slip. However, characteristic and influence on permeability of the aseismic slip is unknown. Therefore, in this study, to clarify the occurrence condition, characteristics and influence on permeability of aseismic slip, injection-induced slip experiment using cylindrical specimen with a 45° tilted tensile fracture was conducted under the condition 200-500 °C.
Gan, Quan (University of Aberdeen / Pennsylvania State University) | Fang, Yi (University of Texas / Pennsylvania State University) | Im, Kyungjae (Pennsylvania State University) | Elsworth, Derek (Pennsylvania State University)
Despite attempts to engineer viable deep reservoirs for the recovery of thermal energy at high enthalpy and mass flow rates - dating back to the 1970s - this goal has been surprising elusive. The record is replete with failed attempts, examples on life support and some successes. The key difficulties are in (i) accessing the reservoir inexpensively and reliably at depth, (ii) in penetrating sufficiently far through the reservoir, and (iii) in stimulating the reservoir in a controlled manner to transform permeability from microDarcy to higher than milliDarcy levels with broad and uniform fluid sweep and (iv) to create and retain adequate fluid throughput and heat transfer area throughout the project lifetime. We discuss key controls on permeability evolution in such complex systems where thermo-hydro-mechanical-chemical and potentially biological (THMC-B) effects and feedbacks are particularly strong. At short-timescales of relevance, permeability is driven principally by deformations - in turn resulting from changes in total stresses, fluid pressure or thermal and chemical effects. We explain features of reservoir evolution with respect to both stable and unstable deformation, the potential for injection-induced seismicity and its impact on both reservoir performance and in interrogating the evolving state of the reservoir.
The estimated thermal resource in the upper 5 km of crust below the US is of the order of 107 EJ. This compares favorably both with the hydrothermal resource at a mere 104 EJ and to the annual energy budget for the US, at ∼100 EJ/year. Recovering even a fraction of this baseload resource would contribute significantly to a new low carbon energy economy.
The intrinsic goal of recovering thermal energy from the shallow crust (∼5 km for Engineered Geothermal Systems) requires that high-fluid-throughput and thermally-long-lived geothermal reservoirs may be universally engineered and developed, at will, and at any geographic location. High-fluid-throughput in traditional basement rocks requires that reservoir permeabilities at depth (∼5 km) must be elevated from the microDarcy to the milliDarcy range - this avoids untenable pumping costs and avoids inadvertently fracturing the reservoir by extreme fluid overpressuring of the heat-exchange fluid. Although fracturing would appear desirable in developing conduits with high-fluid-throughput, it typically violates the second tenet of a desired long thermal life, which
requires that high heat-transfer area is maintained concurrent with high flow rates. This is only feasible if fluid circulation in the reservoir has a broad and even sweep through media with a short thermal diffusion length (small fracture spacing) thus avoiding short-circuiting and damaging feedbacks of thermal permeability enhancement.