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.
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.
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.
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.
A large number of laboratory experiments about the influence of heating or heating-cooling cycles on the mechanical properties of various granites are reviewed. Both scanning electron microscopy (SEM) and particle-based discrete element modeling (DEM) are employed to quantitatively elucidate the mechanisms responsible for temperature-dependent mechanical properties of granites, from a perspective of microcracking. Both SEM observations and DEM simulations give consistent results and show that there exists a temperature threshold beyond which the thermally-induced microcracks increase drastically. Both intergranular and intragranular microcracks are observed in the granites after thermal treatment, and intergranular ones are dominant. A continuous increase in temperature can generally weaken granites, mainly by inducing significant thermal stress and generating tensile microcracks. The weakening of granites after a heating-cooling cycle is due only to the thermally induced microcracks. With increasing grain size the magnitude of Brazilian tensile strength reduction of granites due to thermal treatments becomes small, whereas with increasing heterogeneity in grain size distribution, the magnitude of Brazilian tensile strength reduction of granites due to thermal treatments becomes great. This is because the two competing mechanisms, i.e., the length and number of the thermally induced microcracks in granites.
Since the first enhanced geothermal system (EGS) was conceived at the Fenton Hill project, the United States, in the 1970s, EGS projects have been pursued around the world (McClure and Horne, 2014). EGS projects involve finding vast blocks with high temperature (> ~200 °C) and connected fracture networks. Working fluid (e.g., water or supercritical CO2) is first injected and circulated through the fracture networks in geothermal reservoirs and eventually pumped back to the surface as steam. In the world EGS projects are commonly located in granite rocks with various mineralogical properties (Zhao et al. 2018). The mechanical response of “hot granites” to cooling becomes an important question to geologists and engineers.
Several variants of rate-state equations were considered inapplication to description of laboratory data on block slidingunder normal and shear stresses. Both acoustic emission andstick-slip motion of the block were registered and consideredas an analog of ordinary and slow earthquakes. Various typesof fluids were added to the filler between the moving andstationary blocks. Obtained results on the block sliding werecompared with numerical simulations which were conductedusing several variants of the rate-state equations, and the bestmatching model was chosen for further study. With the helpof that model, the seismic activity induced by fluid injectionduring Basel project was simulated. It was shown, that somelong-term aftereffects of the fluid injection can be explainedby specific value of the interblock stiffness related to thesurround rock stiffness.
Presentation Date: Thursday, October 18, 2018
Start Time: 8:30:00 AM
Location: 210C (Anaheim Convention Center)
Presentation Type: Oral
We consider the problem of identifying geothermal reservoirs in an exploration setting utilizing information from transient electromagnetic (TEM) and magnetotelluric (MT) data. The inversion methodology proposed uses information about the conductive clay cap gained from TEM inversion in the generation of a prior model for Bayesian inversion of 3D MT data. To facilitate the identification of large-scale structures typically associated with geothermal exploration, a level-set type representation of the electric resistivity is utilized. TheMTinversion is performed using the ensemble Kalman filter, which does not require calculation of sensitivities and provides quantification of the uncertainties in the resistivity model. We apply the inversion methodology to synthetic geothermal test cases where three prior models for the geothermal reservoir were used: one small in size, but with the correct center location; another with correct size, but wrong location; and a third with small size and wrong location. The test cases showed that the clay cap was accurately estimated and the reservoir was well approximated, both in terms of shape and location.
Presentation Date: Thursday, October 18, 2018
Start Time: 8:30:00 AM
Location: 213A (Anaheim Convention Center)
Presentation Type: Oral