Drilling Cost Research Articles

Repurposing abandoned wells for geothermal energy: Current status and future prospects

A debate rages as to whether abandoned oil and gas wells have to be sealed to prevent methane leakage – a potent greenhouse gas – or whether the valuable infrastructure can be repurposed for environmental benefit. One viable solution is to repurpose such wells for the recovery of low-grade geothermal energy and simultaneously produce a revenue stream, staunch fugitive emissions and maintain workforce engagement. This avoids the major upfront costs of drilling and significant risks of non-transmissive reservoirs that remain major obstacles in the development of geothermal energy. Regions of extensive hydrocarbon exploration are often close to market and with significant geothermal gradients. Repurposing must accommodate local energy demand, potential markets, existing infrastructure and technical challenges. So far, most studies have been scattered or focused on the viability of converting a specific oilfield. This work integrates the accomplishments and key challenges faced from projects that converted hydrocarbon production in geothermal renewable energy and establish guidelines to assist future projects. Conversion strategies are discussed for open-loop systems with co-production and enhanced geothermal systems and for true closed-loop systems. Five key challenges relate to well selection, data availability, underground infrastructure, well integrity and regulatory factors. Potential challenges in inspection and preparation of these wells in terms of well integrity and productivity with possible remedies are also discussed. Pilot projects and feasibility studies that have been performed worldwide confirm the viability of this concept but at low efficiency, paving the way for future innovations in this area.

Hole Cleaning Performance of V-Shaped Hole Cleaning Device in Horizontal Well Drilling: Numerical Modeling and Experiments

The application of hole cleaning devices can effectively solve the hole cleaning problem during the drilling of horizontal wells. Improving the hole cleaning performance is directly related to subsequent drilling time and cost. In this paper, the solid–liquid two-phase hydrodynamic characteristics under the action of the V-shaped hole cleaning device for drilling horizontal wells were studied experimentally and numerically. The decay law of spiral flow induced by the V-shaped hole cleaning device was obtained numerically using the commercial CFD code “Fluent” by changing the blade rotational speed, blade helix angle, and consistency coefficient of drilling fluid. The helix angle will cause the flow direction of local fluid to deflect. The swirl intensity of spiral flow increases significantly with an increase in rotational speed. The hole cleaning performance was better when the helix angle was from about 10 to 20 degrees. Increasing the fluid consistency coefficient will rapidly make the spiral flow decay, resulting in a shorter effective action distance and a worse hole cleaning effect. The simulation results were validated against the experimental results of the flow loop. Both experimental and simulation results showed that the hole cleaning performance was improved by using the V-shaped hole cleaning device. The very good agreement achieved between the results has presented an opportunity to study the hole cleaning effect of a hole cleaning device in unsteady state conditions. The results will provide theoretical guidance for efficient hole cleaning using V-shaped hole cleaning devices for horizontal well drilling.

ROP Prediction with Supervised Machine Learning; a Case Study

Optimum drilling penetration rate, known as the rate of penetration (ROP) has played a big role in drilling operations. Planning the well ROP always becomes a challenge for drilling engineers to calculate the drilling time needed for the section. Optimum ROP is achieved when the time to drill the section is as planned.
 Many empirical approaches were develop to model the ROP based on the drilling parameters, and might not always match the actual ROP. In some cases, the actual ROP was slower than planned, which may increase the drilling cost, which needs to be avoided.
 Hence, some approaches using artificial intelligent (AI), and supervised machine learning have been develop to overcome it. Supervised machine learning is used to develop a ROP model and ROP prediction for one of the development fields, based only on two wells drilling parameters data. The model was train using Gradient Boosting, Random Forest, and Support Vector Machine. Drilling parameter test data then is used to validate the model. The model of Random Forest shows a good or promising result with R2 of 0.90, Gradient Boosting shows R2 of 0.86, and Support Vector Machine with R2 0.72. Based on the models generated, the Random Forest has shown good trend which could be used for modeling ROP in the future development wells.

Geochemistry and origins of natural gas in the Hong-Che fault zone of the Junggar Basin, NW China

The uplift zone adjacent to the sag is the dominant direction of natural gas migration and accumulation, and the multi-layer source rocks developed in the sag have laid a material foundation for natural gas accumulation. However, owing to the deep burial and high drilling cost of the sag, drilling the source rocks in the sag is challenging, which severely restricts the fine gas-source correlation study of natural gas in the uplift zone. The Hong-Che fault zone is adjacent to the Shawan sag, the natural gas is of various types, and the origin and source of natural gas are unclear. The referential contrast research methods on multi-source and multi-period natural gas are absent, which hinders their subsequent exploration and development. In view of these problems, we analysed the pyrolysis gas of source rocks, along with its composition, including the light hydrocarbon and the carbon isotope of natural gas. The experimental results show that: (1) There are significant differences in the carbon isotopes of ethane in pyrolysis gas from different source rocks, which is one of the research bases of natural gas source analyses. (2) The natural gas in the region is mainly present as kerogen cracking gas. (3) The natural gas in the study area is divided into five types. Type-Ⅰ and type-Ⅱ gases derived from the humic source rocks of the Carboniferous stratum and the Jiamuhe Formation, respectively. Type-Ⅲgas was sourced from the sapropelic source rocks of the Fengcheng Formation. Type-Ⅳ gas was originated from mixed source rocks of the Wuerhe Formation. Type-Ⅴ gas was derived from the mixing of multiple sets of source rocks. (4) The south section of the Hong-Che fault zone has high gas production, and is a favourable exploration target for humic pure gas reservoirs. The slope area near the Shawan sag has better preservation conditions and is a favourable target area for subsequent natural gas exploration activities. These results lay the theoretical foundation for the evaluation and identification of the origins of multi-source and multi-period natural gas in complex areas.

HORIZONTAL WELL PERFORMANCE MODELLING USING PSEUDOWELL TECHNIQUE

The potential improvement of horizontal productivity has been recognized since mid 1950s, where horizontal well allows longer flow interval hence higher flow rate with lower pressure drawdown. Such remarkable productivity improvement has fascinated the great interest of petroleum industries around the world to fit the role of effective field development strategy. The objective is to reduce the overall cost of field development. In the case of offihore oil fields, the horizontal well drilling is desired to eliminate required number of vertical wells and utilizing of expensive sub-sea technology. The continuous development and application of horizontal well drilling technologies have been reported in many publications, Nowadays, the horizontal well drilling and completion with complex trajectory is possible. However, the costs required by horizontal well drilling and completion is still considerably more expensive than the vertical one. The future needs of horizontal well drilling tend to arise depending on the economical aspect by means the horizontal well productivity outweigh the incremental drilling and completion costs. An adequate method is required to estimate it's expected productivity to determine the economic feasibility. This paper proposes a horizontal well performance modeling by the concept of pseudowell technique.

Investigation on the Tool-Rock Interaction Using an Extended Grain-Based Model

The poor drill-ability of rock in deep hard formation leads to the problems of low rate of penetration (ROP) and high drilling cost. A detailed understanding of the rock-tool interaction is of great significance for improving the rock breaking efficiency and optimizing the cutting parameters. For this purpose, this paper establishes a numerical model of heterogeneous granite which considers the influence of mineral distribution and real grain structure. The fracture behaviors of granite under tool cutting and indentation are investigated subsequently. It is found that there are always four kinds of microcracks in granite, intragranular tensile crack, intragranular shear crack, intergranular tensile crack and intergranular shear crack, among those four crack types, the intergranular tensile crack and intragranular shear crack are dominated, almost no intergranular shear cracks occur. Lateral pressure has no great influence on the volume of cutting chips in rock cutting, but is the direct factor that affects the rock-breaking efficiency in rock indentation. The initiation and propagation of radial cracks will be obviously inhibited in large lateral pressure, and the number of radial cracks will decrease sharply, resulting in low rock-breaking efficiency. Lateral pressure seems to have little effect on the indentation force, the possible reason for this lateral pressure insensitivity is because the far-field lateral pressure has less influence on the indenter tip around field than the existence of free surface. The research results can provide the basis for improving granite rock-breaking efficiency and optimizing rock-breaking tools to a certain extent.

Design strategy and techno-economic optimization for hybrid ground heat exchangers of ground source heat pump system

This study aimed to formulate an accurate design strategy for hybrid ground heat exchanger (HyGHE) of ground source heat pump system and optimize HyGHE size based on techno-economic analysis. First, to analyze the thermal performance of the HyGHE system, a detailed heat transfer numerical model of borehole heat exchanger and horizontal ground heat exchanger was proposed. Then, a novel techno-economic model was employed to assess the economic efficiency of the foregoing system. Subsequently, the design optimization model of the HyGHE system was developed to determine the optimal shave factor (α and β), building load distribution scheme, and HyGHE size. Finally, sensitivity analyses were implemented to determine the optimal design under different conditions. The results reveal that the costs of borehole drilling, pipe, and equipment account for approximately 80% of total capital investments of the HyGHE system. The system initial costs increase with α and can reach 91,385.11 CNY when α = 1.00. In contrast, its annual operational costs first decrease and then increase with increasing α. For the fundamental case, the thermal and economic performance levels of the HyGHE system improve with decreasing α. The optimal design is more sensitive to the unit prices of borehole drilling, pipe, and excavation.

Improving spatial characterization of buried bedrock valleys through airborne frequency-domain electromagnetic, residual magnetic, and surface resistivity measurements

The development of a three-dimensional (3D) hydrogeologic site model requires detailed knowledge of an area's hydrostratigraphy, information typically obtained from core logs, historical well records, outcrop mapping, and/or surface geophysics. Due to the high cost of drilling, a 3D model may rely on various statistical techniques to interpolate lithological boundaries between points located tens of kilometers or more apart. This situation can result in poorly constrained or simplified lithostratigraphic models, with under-sampled features such as karst and buried bedrock valleys. The non-invasive nature of airborne geophysical surveys combined with its dense sampling capability can fill critical data gaps. This study evaluates the capacity of a helicopter borne frequency-domain electromagnetic (FDEM) and residual magnetic survey using the Resolve™ system over a buried bedrock valley incised in a multi-layered dolostone aquifer within a complex glaciated environment in an urban/agricultural region of southern Ontario, Canada. The resulting airborne data was evaluated against two high-resolution ground-based electrical resistivity transects oriented orthogonal to the valley, alongside a published Quaternary geological model. A comparison between our local geophysically-based model and the regional geological model shows that the airborne electromagnetic surveys can markedly improve characterization of bedrock valley morphology and Quaternary sedimentary unit architecture that is comparable to that obtained using high-resolution surface-based electrical resistivity measurements with 10 m electrode spacing. The scale of heterogeneity that can be resolved by the airborne survey reveals the level of petrophysical variability that can be seen within the valley infill. Our study demonstrates the potential of airborne FDEM surveys in semi-urban agricultural environments where detailed characterization of Quaternary sediment architecture and bedrock topography is needed to inform 3D groundwater flow system variability.

The role of pore pressure and its prediction in deep geothermal energy drilling – examples from the North Alpine Foreland Basin, SE Germany

Pore pressure prediction is a well-developed key discipline for well planning in the hydrocarbon industry, suggesting a similar importance for deep geothermal wells, especially, since drilling cost is often the largest investment in deep geothermal energy projects. To address the role of pore pressure prediction in deep geothermal energy, we investigated pore pressure-related drilling problems in the overpressured North Alpine Foreland Basin in SE Germany – one of Europe's most extensively explored deep geothermal energy plays. In the past, pore pressure was mainly predicted via maximum drilling mud weights of offset hydrocarbon wells, but recently more data became available, which led to a re-evaluation of the pore pressure distribution in this area. To compare the impact of pore pressure and its prediction, 70% of all deep geothermal wells drilled have been investigated for pore pressure-related drilling problems and two deep geothermal projects are given as more detailed examples. Thereby, pore pressure-related drilling problems were encountered in one third of all wells drilled, resulting in several side-tracks and an estimated drilling rate decrease of up to 40%, highlighting the importance of accurate pore pressure prediction to significantly reduce the cost of deep geothermal drilling in overpressured environments. Thematic collection: This article is part of the Geopressure collection available at: https://www.lyellcollection.org/cc/geopressure

Multi-Objective Optimization of Drilling Trajectory Considering Buckling Risk

Directional drilling involves three sections—vertical, curved, and horizontal—and is used for drilling offshore wells and mining unconventional resources. The initial design of a well trajectory is important because the total length of the well trajectory is associated with the drilling cost; furthermore, the drag force and torque may cause buckling and damage the drill pipe. The well trajectory should be optimized considering the length and load of drill pipes. In this study, a new method of optimizing directional well trajectory is used to formulate the objective function considering the length, drag, and torque. To verify the applicability of this method, we applied it to an actual oil well and a theoretical oil well. The results obtained show that the use of the proposed method in the initial design of drilling trajectory can reduce the torque by up to 15%, drag by 2.6%, and length by 8.5% for the two models used in this study. This method is safer as it reduces the risk of buckling compared to the design that relies on the previous designer’s experience, and it reduces the trajectory length; thus, it can save time and costs of drilling.

Application of multi-attribute matching technology based on geological models for sedimentary facies: A case study of the 3rd member in the Lower Jurassic Badaowan Formation, Hongshanzui area, Junggar Basin, China

Regarding high drilling costs, an effort should be made to substantially reduce the drilling operation. To achieve this goal, exploration and development stages should be carried out precisely with maximum information acquired from the reservoir. The use of multi-attribute matching technology to predict sedimentary system has always been a very important but challenging task. To resolve the challenges, we utilized a quantitative analysis method of seismic attributes based on geological models involving high resolution 3D seismic data for sedimentary facies. We developed a workflow that includes core data, seismic attribute analysis, and well logging to highlight the benefit of understanding the facies distribution in the 3rd Member of the Lower Jurassic Badaowan Formation, Hongshanzui area, Junggar Basin, China. 1) Data preprocessing. 2) Cluster analysis. 3) RMS attribute based on a normal distribution constrains facies boundary. 4) Mapping the sedimentary facies by using MRA (multiple regression analysis) prediction model combined with the lithofacies assemblages and logging facies assemblages. The confident level presented in this research is 0.745, which suggests that the methods and data-mining techniques are practical and efficient, and also be used to map facies in other similar geological settings.

Ilmenite Inclusion: A Solution towards Solid Sagging for Hematite-Based Invert Emulsion Mud

The sagging tendency of hematite in drilling mud is a common challenge occurring at high-pressure and high-temperature (HP/HT) applications. This work studies the performance of hematite-based invert emulsion mud for HP/HT conditions and provides a solution to prevent the hematite settlement using a combination of ilmenite with hematite. Practical mud formulation was utilized over a range of ilmenite/hematite ratios (0/100, 20/80, 40/60, and 50/50%) to study sagging behaviour. From the sag tests, the optimum combination proportion was determined. Thereafter, the density, emulsion stability, rheological and viscoelastic properties, and filtration conduct for the formulated mud were evaluated. The experiments were conditioned as per the standards of the American Petroleum Institute. The obtained results of sagging experiments indicated that including 50% of ilmenite mitigated the hematite settling and reduced the sag tendency towards the safe range. A slight drop (4%) in mud weight was noticed upon adding the ilmenite, whereas the emulsion stability was enhanced from 551 to 574 volts with the 50% ilmenite content. The rheology and viscoelasticity measurements showed that 50/50% combination improved the yield point (YP) by 50% with a trivial 1 cP increment on plastic viscosity (PV), hence enhancing the YP/PV ratio by 46%. Also, the gelling strength was enhanced resulting in flat rheology and better gel structure. The filtration behaviour of 50% ilmenite mud was improved compared to blank hematite as it resulted in 21, 15, and 17% reduction on the filtrated volume, filter cake weight, and thickness, respectively. This study provides a solution for hematite sagging issue at HP/HT using combined weighting agents, which contributes to enhancing the mud stability and avoiding several well control issues and related operational and technical challenges that eventually will economize the drilling cost and time.

БЕНЧМАРК-АНАЛИЗ РИСКОВ НЕДОСТИЖЕНИЯ ПРОЕКТНЫХ ПАРАМЕТРОВ ТЕХНИКО-ЭКОНОМИЧЕСКОГО ОБОСНОВАНИЯ ОТРАБОТКИ МЕСТОРОЖДЕНИЯ

The mine development project is a set of works, which, due to the uniqueness of mining and geological cond卜 tions, territorial location, climatic factors, lack of the necessary infrastructure, will be subject to a high degree of project risk. The aim of the work is to increase the implementation efficiency of the field development project based on a comparative analysis of the main technical and economic indicators with world industry leaders. Ma- teria/s and methods. Based on the model of the mineral resources of the deposit and the comparative analysis carried out with a reference base with more than forty leading world deposits (benchmarking), a strategic anal-ysis of the main technical, technological, organizational and economic parameters of open pit development has been carried out. The risk analysis, the input parameters used in the preliminary feasibility study of the project are adjusted and updated. The choice of the limiting open pit shell has been carried out, the problem of choosing the mining method and parameters of the equipment used has been solved, and the analysis of the optimal height of the open pit bench and the stages of development of technological blocks of the field have been carried out. Results. The obtained values of the main technical and economic indicators have formed the basis for the formation of a mining plan, as well as an assessment of operating and capital costs, taking into account risk factors. The following most significant risks are identified: availability of staff with relevant experience and competencies required to implement the mining plan; oxidation of long-term storage ore warehouses, which leads to a decrease in mineral extraction rates; high diesel and electricity costs. Conclusions. Based on the identified risk factors, capital and operating costs have been determined and adjusted for the level of energy consumption, the cost of drilling and blasting operations, control of the content of the useful component, loading, maintenance costs, labor costs and general costs

Rate of penetration prediction while drilling vertical complex lithology using an ensemble learning model

The rate of penetration (ROP) accounts for a substantial portion of the overall drilling cost. The drilling optimization process, which mostly involves the adjustment of the mechanical drilling parameters, is therefore of prime importance in ensuring efficient drilling. However, drilling formations with assorted types of lithology necessitate the involvement of more parameters to reduce uncertainty and enhance confidence when predicting the ROP. The objective of this paper is to introduce an ensemble model based on random forest (RF), in which artificial neural network (ANN), and adaptive neuro-fuzzy inference system (ANFIS) are the base learner models, to predict the ROP across different lithological formations In this study, two types of actual field data of Well-1 were employed to build the model: (i) mechanical drilling parameters collected from real-time sensors allocated at the rig site, and (ii) petrophysical properties obtained from conventional well logs. Well-2 with more than 2300 unseen data points was used to compare the capability of the base learners (i.e., ANN and ANFIS), standalone RF, and RF-meta model in predicting the ROP with two of the earliest published ROP empirical models (Maurer's and Bingham's models). The results showed that the RF-meta model outperformed the base learners and Maurer's and Bingham's empirical models in predicting the ROP in Well-2 with a low absolute average percentage error (AAPE) of 7.8 % and a high coefficient of determination (R2) of 0.94.

Artificial neural networks-based correlation for evaluating the rate of penetration in a vertical carbonate formation for an entire oil field

The rate of penetration (ROP) is a critical factor affecting the process of oil well drilling optimization and the total drilling cost. This work introduces an empirical correlation extracted from the learned artificial neural networks (ANN) to assess the ROP across a vertical carbonate formation from five surface drilling parameters measurable through real-time sensors. The ANN was built based on real 220 datasets obtained from eight wells. The data from five of these wells were used to train the ANN model. Several sensitivity analyses were conducted on the model's parameters to achieve the best combination of these parameters. To enable real-time assessment of the ROP, a correlation from the leaned ANN model was extracted, which was tested on 92 datasets from the same training wells while unseen datasets from another three wells were used for validating the empirical correlation. The results showed that the ANN was effectively predicted the ROP with an average absolute percentage error (AAPE) of only 4.34% for the training data. Using the developed equation, the ROP was assessed for the validation data with an average AAPE of 6.75%.

Deep Learning-Accelerated 3d Carbon Storage Reservoir Pressure Forecasting Based on Data Assimilation Using Surface Displacement from Insar

Fast forecasting of reservoir pressure distribution in geologic carbon storage (GCS) by assimilating monitoring data is a challenging problem. Due to high drilling cost, GCS projects usually have spatially sparse measurements from wells, leading to high uncertainties in reservoir pressure prediction. To address this challenge, we propose to use low-cost Interferometric Synthetic-Aperture Radar (InSAR) data as monitoring data to infer reservoir pressure build up. We develop a deep learning-accelerated workflow to assimilate surface displacement maps interpreted from InSAR and to forecast dynamic reservoir pressure. Employing an Ensemble Smoother Multiple Data Assimilation (ES-MDA) framework, the workflow updates three-dimensional (3D) geologic properties and predicts reservoir pressure with quantified uncertainties. We use a synthetic commercial-scale GCS model with bimodally distributed permeability and porosity to demonstrate the efficacy of the workflow. A two-step CNN-PCA approach is employed to parameterize the bimodal fields. The computational efficiency of the workflow is boosted by two residual U-Net based surrogate models for surface displacement and reservoir pressure predictions, respectively. The workflow can complete data assimilation and reservoir pressure forecasting in half an hour on a personal computer.

Experimental and numerical study of cuttings transport in inclined drilling operations

Directional drilling has become popular in recent decades in both onshore and offshore operations due to reduced drilling costs and improved recovery. In a directional well drilling operation, drill cuttings tend to settle down at the lower side of the inclined annular section. If the generated cuttings are not removed from the hole section properly, it causes a cuttings bed formation in the annular section. Different drilling related problem such as poor rate of penetration, excessive torque and drag, increase differential sticking often associated with a poor hole cleaning which eventually lead to increase in non-productive time (NPT). Therefore, the success of inclined well drilling operation largely depends on effective cleaning of drill cuttings from the annular section. A variety of parameters, including the fluid rheology, mud velocity, cuttings size, drill pipe rotation and drill pipe inclination generally influence the cuttings transport performance. Optimization of these drilling parameters is crucial to ensure proper hole cleaning. In this study, a Computational Fluid Dynamics (CFD) model for the inclined well section is used to investigate the cuttings transport efficiency (CTE). An Eulerian-Eulerian multiphase flow model is proposed and validated with lab scale experimental data. The experiments were performed in a 6.16-m-long annular test section having an outer pipe diameter of 4.5-inch and an inner pipe diameter of 2.5-inch. The setup is equipped with Electrical Resistance Tomography (ERT) system to measure the instantaneous solid volume fraction and a visualization section. A non-Newtonian Heschel-Bulkley (HB) fluid was used as drilling mud and solid glass beads of 2.50 mm–3.00 mm were used as cuttings in the experiment. This study shows a good agreement in visualization of mechanistic three-layer model of cuttings transport in terms of ERT data from experiment and CFD simulation. The validated CFD model is used to perform 5- Factors factorial design and analysis of variance (ANOVA) study. ANOVA shows that the interaction effects of mud velocity-cuttings size, mud velocity-inclination are statistically significant. Finally, this study proposed a statistical model to estimate the CTE of an inclined well considering the two factor and three factor interactions among the variables. Also, the model shows that drill pipe rotation has negligible effect in improving cuttings transport efficiency in the inclined well. The proposed model also reveals that cuttings size and fluid velocity account for 78% contribution in the transport efficiency for an inclined well. Furthermore, an Artificial Neural Network (ANN) method is used to verify the contribution of lower order interaction in the statistical model. Though empirical model shows few lower order two factor interactions (fluid rheology -cuttings size, fluid rheology-inclination), and three factor interactions (velocity-cuttings size-inclination, fluid rheology-cuttings size-inclination); ANN model shows that lower order interaction are significant in model prediction and should not be ignored. The findings of this study can help in better understanding the interaction behaviour among drilling parameters and optimized cuttings transport efficiency in the inclined drilling operation for a wide variety drilling parameters.

Numerical Modeling of the Effects of Pore Characteristics on the Electric Breakdown of Rock for Plasma Pulse Geo Drilling

Drilling costs can be 80% of geothermal project investment, so decreasing these deep drilling costs substantially reduces overall project costs, contributing to less expensive geothermal electricity or heat generation. Plasma Pulse Geo Drilling (PPGD) is a contactless drilling technique that uses high-voltage pulses to fracture the rock without mechanical abrasion, which may reduce drilling costs by up to 90% of conventional mechanical rotary drilling costs. However, further development of PPGD requires a better understanding of the underlying fundamental physics, specifically the dielectric breakdown of rocks with pore fluids subjected to high-voltage pulses. This paper presents a numerical model to investigate the effects of the pore characteristics (i.e., pore fluid, shape, size, and pressure) on the occurrence of the local electric breakdown (i.e., plasma formation in the pore fluid) inside the granite pores and thus on PPGD efficiency. Investigated are: (i) two pore fluids, consisting of air (gas) or liquid water; (ii) three pore shapes, i.e., ellipses, circles, and squares; (iii) pore sizes ranging from 10 to 150 μm; (iv) pore pressures ranging from 0.1 to 2.5 MPa. The study shows how the investigated pore characteristics affect the local electric breakdown and, consequently, the PPGD process.

Comparative study of hybrid ground source heat pump in cooling and heating dominant climates

The ground source heat pump system (GSHP) has been an accepted technology to provide energy efficient and renewable air conditioning to the buildings. However, imbalanced heating and cooling load during the winter and summers especially in the regions with heating and cooling dominant climates may degrade the performance of the system over a long-term operation. Hybrid GSHP system which uses supplemental energy sources such as solar panel or cooling tower can balance the imposing load on the ground heat exchanger (GHE) and benefits the system by minimizing the GHE length in short-term and improves the overall performance in long-term. This research presents a study of application of hybrid GSHP system with an intention to compare its applicability in the regions with dominant heating and cooling loads. In this study, a student office and an actual heat pump system in Akita City, northern Japan was modeled in TRNSYS software and was validated using in-situ measured data. The hybrid system which coupled with a supplemental heating and cooling source devices was simulated to test its viability for the different heating and cooling loads in different regions within the country. The results revealed that hybrid system plays an effective role in both climates to balance the load on GHE, keeps constant the soil temperature, and consequently improves the long-term performance. Moreover, in short-term, it can reduce the GHE length and decrease drilling cost based on the meteoroidal condition of the region such as solar radiation. For instance, the GHE length was reduced to around half in cooling dominant region using cooling tower, while it was negligible in heating dominant region.

Delaware Basin Case History Details Economic Benefit of Water-Recycling Program

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204166, “Turning Produced Water Into an Asset: A Delaware Basin Case History,” by Dustin Aro, SPE, and Steven Fowler, SPE, Precision Petroleum Solutions, prepared for the 2021 SPE Hydraulic Fracturing Technology Conference and Exhibition, held virtually 4–6 May. The paper has not been peer reviewed. Well completion operations are affected by freshwater procurement costs starting at approximately $0.75/bbl. Regardless of final fracturing design, water consumption during fracturing operations typically exceeds 500,000 bbl, or $375,000 per well at the time of writing. Significant value exists for recycling produced water by an on-lease pit that can be used for future fracturing operations. The case history outlined in the complete paper explores a multiwell sectional development in the Delaware Basin by a small operator that reduced drilling and completion costs, along with lease operating expenses, by turning undesirable produced water into an asset. Regulatory Considerations Because the Delaware Basin straddles two states, it is important to understand the guidelines and processes of pursuing produced-water recycling operations in Texas as opposed to New Mexico. The operations discussed were executed and managed on the Texas side. While contractor familiarity can be beneficial during the planning stages, the operator also must be well-versed in applicable regulations. It is advisable to consult with legal counsel regarding liability should an unplanned discharge event occur. Lease Development History Before the beginning of initial completions operations, three freshwater wells were drilled on-lease with the intention of use for fracturing operations. The flow rate from the three wells was insufficient to keep up with fracturing operations by an aboveground storage tank (AST). A large-volume fracturing pit was not constructed. The initial completion on Well 1, targeting the Wolfcamp C bench, was executed primarily with fresh water sourced from a third-party pit that was transferred to a nearby AST. During production, Well 1 maintained a high water cut (greater than 90%) and produced a significant amount of water over time. Additional infrastructure would be required to fully exploit the existing freshwater wells as a source for future completions activity. Operator break-even treatment costs have been determined to be the most favorable when using a centralized pipeline water-management program. A pit would act as a centralized gathering point with temporary pipeline infrastructure for water-transfer purposes. An internal economic analysis was undertaken to determine construction costs for a pit that could accommodate 500,000 bbl or 1,000,000 bbl of fresh water. The option of constructing a pit that could handle produced water also was included for comparison.