Types Of Wells Research Articles

A Mixed Methods Approach to Understanding the Public Health Impact of a School-Based Citizen Science Program to Reduce Arsenic in Private Well Water.

Exposure to arsenic (As) in well water is a well-documented public health issue for Maine and New Hampshire, as well as for other states in the United States and abroad. Arsenic contamination of well water in these locations is primarily attributed to metasedimentary bedrock that leaches As into groundwater. However, As can also enter groundwater reserves from soils contaminated by the historical use of arsenical pesticides. Approximately half of the households in Maine and New Hampshire rely on private wells, many of which have elevated As. Arsenic exposure has been associated with an increased risk of cancer, cardiovascular disease, reduced infection resistance, and lower intelligence quotient in children. Despite these known health impacts, well water testing and treatment are not universal. We have approached the problem of low well water testing rates in Maine and New Hampshire communities by developing the All About Arsenic (AAA) project, which engages secondary school teachers and students as citizen scientists in collecting well water samples for analysis of As and other toxic metals and supports their outreach efforts to their communities. We assessed this project's public health impact by analyzing student data relative to existing well water quality datasets in both states. In addition, we surveyed private well owners who contributed well water samples to the project to determine the actions taken to mitigate As in well water. Students collected 3,070 drinking water samples for metals testing, and 752 exceeded New Hampshire's As standard of . The AAA data has more than doubled the amount of information available to public health agencies about well water quality in multiple municipalities across both states. Students also collected information about well types and treatment systems. Their data reveal that some homeowners did not know what type of wells they had or whether they had filtration systems. Those with filtration systems were often unaware of the type of system, what the system was filtering for, or whether the system was designed to remove As. Through interviews with pilot survey participants, we learned that some had begun mitigating their exposure to As and other toxic metals in response to test results from the AAA project. A school-based approach to collecting and analyzing private well water samples can successfully reach communities with low testing rates for toxic elements, such as As and other metals. Importantly, information generated through the program can impact household decision-making, and students can influence local and state policymaking by sharing information in their communities. https://doi.org/10.1289/EHP13421.

Geothermal resource evaluation in the Sichuan Basin and suggestions for the development and utilization of abandoned oil and gas wells

In this paper, the potential seven sets of geothermal resources in the Sichuan Basin were evaluated by using a method for rapidly calculating geothermal resources in the sedimentary basins by multi data fusion, and suggestions on geothermal development and utilization are made based on the basic characteristics of abandoned wells in the oil and gas fields. The results show that the Sichuan Basin is rich in geothermal resources. The total resources of 7 sets of thermal reservoirs reach 4.26 × 1013 GJ, of which the Qixia-Maokou Formation has the largest potential geothermal resources, reaching 1.36 × 1013 GJ. The Permian Qixia-Maokou Formation in southern Sichuan Basin has the conditions to prioritize the development of geothermal resources and has the characteristics of the highest temperature of formation water and the largest current and cumulative water production. At the same time, according to the formation temperature of abandoned oil and gas wells, they are divided into two types of wells, and different geothermal resource utilization methods are proposed. The research results can provide a model for the evaluation of geothermal resources in sedimentary basins and a resource basis for the development of geothermal resources in the Sichuan Basin.

Geospatial analysis of groundwater arsenic and fluoride in Quaternary aquifers of southern Ontario, Canada

The geological setting of an area plays a critical role in the transfer and ultimate distribution of hydrochemical constituents present in groundwater. In southern Ontario, Canada, the present physiography was significantly influenced by glacial processes during the Quaternary period. The heterogeneous nature and complex pattern of shallow subsurface glacial overburden sediments, likely affect the fate of different groundwater constituents. In this study, arsenic (As) and fluoride (F−) concentrations from 515 water wells, that are constructed within overburden sediment, were analyzed with the physiographic map of southern Ontario along with other related variables. Geospatial mapping and several spatial statistical analyses were performed to examine the possible geological influence on As and F− distribution and water-well susceptibility at a regional scale. Key findings suggest four physiographic settings were significant variables influencing the distribution of As and F− in differently constructed bored/dug and drilled wells. Bored/dug wells in Bevelled Till Plains and bored/dug wells in Undrumlinized and Bevelled Till Plains were found to be relatively susceptible to As and F− contamination respectively. In contrast, bored/dug and drilled wells in Drumlinized Till Plains and Drumlins and drilled wells in Sand Plains seemed to be relatively safe from F− and As respectively. The statistical regression analyses suggested that other variables, such as the application of phosphate fertilizer and the textures of till, influenced the spatial distribution of As and F− as well as which types of wells (bored/dug or drilled) were impacted. The geospatial mapping and statistical cluster analysis indicated that the possible sources of elevated As and F− in drilled wells are the clasts of underlying bedrock. The relationship between physiographic settings and impacted overburden wells in southern Ontario provides planners with an approach to water-well susceptibility assessments at the regional scale, which in turn can guide further local analysis for water resource management.

Hydrohelical ESP Gas Separator Increases Flow Range, Improves Reliability

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214723, “New High-Performance ESP Gas Separator,” by Barry Nicholson, SPE, and Scott R. Harryman, SPE, Oxy, and Donn J. Brown, SPE, Halliburton, et al. The paper has not been peer reviewed. _ The complete paper presents research, design, and field testing of a new type of mechanical gas separator for electrical submersible pump (ESP) systems that increases operating flow range and separation efficiency while decreasing erosion problems and improving reliability. The hydrohelical separator system has been proved effective in different types of wells. Background Several methods and techniques exist for avoiding gas in ESPs, including inverted shrouds, passive separators, mechanical gas separators, and tandem gas separators. Most share the limitations of limited flow capabilities and reduced performance at higher total flow rates. The many variables associated with complex two-phase flow behavior, internal and external pressure variations, separation methods, velocity and viscosity of fluids, effect of the pump bolted above, inherent erosion issues, and single vs. tandem designs add to the challenge of basic mechanical gas-separator operation. In 2016, a program was initiated that featured investment in both experienced personnel and advanced testing technology to unravel the aforementioned challenges and improve understanding of the operation of downhole mechanical gas separation. The team investigated innovative methods of testing and created a transparent testing system that allowed visual observation of individual internal flow regimes as well as component performance. Using a combination of high-speed photography, computational fluid dynamics validation, and specialized instrumentation, every component of a mechanical separator system was enhanced for higher flow capabilities, improved separation efficiency, and higher reliability for a variety of downhole conditions. The result was the development of a new type of mechanical gas separator for ESP use. Development Most gas separators ingest multiphase fluid into a separation chamber, separate the gas and liquid phases, eject the separated gas phase into the well annulus, and provide sufficient liquid phase fluid to the pump to enable efficient pumping. Existing designs vary, but they share separation methods that result in decreased efficiency at higher flow rates and low maximum flow rates compared with the pumps they feed. The hydrohelical gas separator is the first downhole, dynamic gas-separator design improvement in more than 30 years designed to address these deficiencies (Fig. 1). The design was aimed at the following main objectives: - Increase total fluid flow rate through the separator - Maximize efficiency of every internal and external component of the system - Reduce erosion characteristics common in traditional gas-separator designs - Improve reliability The design of the hydrohelical gas separator is based on a stationary helical vortex inducer and pump stages that enable movement of large quantities of fluid while remaining immune to gas locking. The stationary helical vortex inducer design enables increased efficiency and flow rate through the separator by reducing turbulence in remixing regions within the helical inducer and separation chamber.

An open source experimental framework and public dataset for vibration-based fault diagnosis of electrical submersible pumps used on offshore oil exploration

An Electrical Submersible Pump (ESP) is an important equipment used in the industry for lifting liquids in various types of wells. An ESP is widely used in the oil industry for offshore exploration. Detecting a faulty ESP before installation is a predictive maintenance measure in order to extend its operational time. Machine learning fault diagnosis is an effective way for performing this task. Machine learning fault diagnosis algorithms are highly dependent of the availability of an appropriate problem dataset. This paper describes in detail the problem of ESP fault diagnosis and the ESPset dataset, a real-world and public dataset for vibration-based fault diagnosis of electrical submersible pumps used on offshore oil exploration. In addition, the paper also proposes an experimental framework for adequately comparing research works based on the ESPset dataset and defines benchmark classifiers and respective results as referential to the fault diagnosis research community. The framework considers the fact that some subset of samples are not drawn independently, and therefore, proposes a cross-validation sampling strategy that mitigates the similarity bias among samples. Indeed, this work shows that a conventional k-fold cross-validation may lead to a clear overestimation of the average performance. This fact is supported by results which show that the best classification model drops from a mean F-measure of 0.887 to 0.733 when removing the similarity bias from the data.

Novel approach to roof rainwater harvesting and aquifer recharge in an urban environment: Dry and wet infiltration wells comparison

In urban environments there is a severe reduction of infiltration and groundwater recharge due to the existence of large impervious areas. During rain events, large volumes of water that could have recharged groundwater and surface water bodies are diverted into the municipal drainage system and lost from the freshwater storage. Moreover, extreme rain events impose high peak flows and large runoff volumes, which increase the risk of urban floods. Recent studies have suggested the use of rainwater harvesting for groundwater recharge, as a plausible solution for these challenges in dense urban environments. While the benefits of this approach are well understood, research on its practical, engineering, and hydrological aspects is relatively limited. The objective of the present study was to examine the use of infiltration wells for groundwater recharge with harvested rainwater collected from building rooftops under Mediterranean climate conditions. Two types of wells with similar hydraulic and technical properties were examined: a well that reaches the groundwater (wet well); and a well that discharges the harvested water into the unsaturated zone (dry well). Infiltration capacities of the wells were compared in controlled experiments conducted during summer months, and in operational recharge of harvested rainwater, during winter. Both dry and wet wells were found to be suitable for purposes of groundwater recharge with rooftop-harvested rainwater. Infiltration capacity of the wet well was about seven times greater than the infiltration capacity of the dry well. While the infiltration capacity of the wet well was constant throughout the entire length of the study (∼10 m3/h/m), the dry well infiltration capacity improved during winter (from 0.5 m3/h/m to 1.5 m3/h/m), a result of development of the dry well with time. Considering Tel-Aviv, Israel, as a case study for a dense modern city in a Mediterranean climate, it is demonstrated herein that the use of infiltration wells may reduce urban drainage by ∼40 %.

Hydrogeochemistry and indicators of flowback and produced water from wells that are hydraulically fractured with recycled wastewater: A case study of the Changning gas field in the Sichuan Basin

With the increasing number of shale gas wells being hydraulically fractured with recycled flowback and produced water to reduce the consumption of fresh water, geochemical indicators of hydraulic fracturing flowback fluids (HFFFs) from such wells need to be found to evaluate the potential pollutants caused by shale gas development. To fill this knowledge gap, we analysed 64 HFFF samples from 3 Changning wells (fracked with recycled wastewater) to form a time series and compared them to HFFF samples from 3 Weiyuan wells (fracked with fresh water). We also made comparisons of HFFFs from two types of wells in the Appalachian Basin with reported data. The results indicated that regardless of the fracturing fluid being used, the water‒rock reaction caused by the hydraulic fracturing process resulted in the release of exchangeable phase elements, such as lithium, boron, with relatively depleted δ7Li and δ11B, and strontium with relatively enriched 87Sr/86Sr values on the shale surface, into the HFFFs. The composition of the injected fracturing fluid affected the strength of the water‒rock reaction, but the effect is negligible, as the fracturing process can still form the unique Sr, Li, and B isotope ratios of the HFFF. Thus, the elemental signatures (B/Cl and Sr/Cl) and isotopic fingerprints (δ11B, δ7Li, and 87Sr/86Sr) derived from HFFFs can be used to distinguish between HFFFs from wells hydraulically fractured by either fresh water or recycled wastewater and flowback water from conventional oil and gas wells. The results are important for the environmental evaluation of the large number of wells being fracked with recycled wastewater each year.

The mobilization mechanism of low oil saturation reservoirs

After fracturing with a guar fluid system in Chang 8 oil reservoir, some wells have high oil production, and some have low production and even only produce water. Therefore, a comparative study is carried out in oil-producing and water-producing wells. The results show that: ① Organic wax adsorbed in oil-producing and water-producing well core pores accounts for 95.39% and 56.67%, respectively, making wells strong oil-wet. A certain proportion of inorganic salts and some other oil-wet organic compounds exist in water-producing wells. ② Under the reservoir conditions, the oil wettability of the water-producing well core is strong, and its original formation wettability is also oil-wet. The original wettability of the oil-producing well formation is water-wet, with oil production capacity. ③ The core residual oil saturation using the guar fluid is 24.7%–29.87%. This results in no oil phase permeability or difficulty to mobilize oil in most oil reservoirs. ④ Forced displacement can mobilize oil in large pores and has a significant effect in producing well, with mobilization efficiency of 53.49%. This article elucidates the wettability formation and crude oil mobilization mechanism of two types of wells, providing direction for the development of this type of reservoir.

Современные подходы к реализации проектов по бурению скважин различной классификации на разных стадиях геолого-разведочных работ

The problem of obsolescence and irrelevance of the standard classification of drilling wells for the intended purpose and a new interpretation of this classification within the framework of modern reality are considered. It is noted that the search for new ways to obtain information during geological exploration leads to the understanding that drilling some types of wells is already completely impractical. In the current situation, projects should be implemented that, on the one hand, will ensure the solution of the set geological tasks, on the other hand, minimize the costs of drilling wells, reduce industrial and environmental risks, with the unconditional receipt of the entire set of required geological information. The complex of works applied in the waters of the inland seas, for the purpose of prospecting, exploration and development of oil and gas fields, can become an example of rational money savings and the efficiency of geological data collection. Currently, the share of large structural deposits of simple structure is completely insignificant, and there are practically no promising oil and gas-bearing areas on land. Current realities are such that geological exploration works penetrate deep horizons of the Earth's crust with a complex geological structure and cover oil and gas-bearing regions located in remote and remote parts of the land. The complex implemented at sea may well be applicable for such sites and will successfully compensate for anachronistic drilling methods.

SOME ASPECTS OF THE GAS WELL TESTING PROCEDURES

The article discusses the basic concepts of designing and testing gas wells. The need to increase the selection of hydrocarbons determines the relevance of creating an information array of data on the reservoir and the fluids that saturate it. To collect information, the results of studies of the bottomhole zone of wells, its drainage zone and the interwell space of the reservoir are analyzed. According to the status, the studied wells are divided into operating and stopped for the period of research. According to the type of wells, production and injection wells are distinguished. In the first, the inflow curve is taken for various well operation modes (IPR). Secondly, the dependence of pressure change during shutdown of a working well (PBU) is analyzed. These studies can be carried out both in production and injection wells. To study well clusters and evaluate the interwell space, the methods of interference testing and the method of pulse studies are used. Information on hydrodynamic studies is provided. Note that the studies carried out in wells can be divided into two large groups. The first one is hydrodynamic studies (well test) which involves carrying out various tests to establish the characteristics of the rock that makes up the reservoir, as well as the properties of the fluid that saturates the porous medium. As a result of the studies, such parameters as permeability, porosity, average reservoir pressure, and degree of reservoir heterogeneity (presence of a screening fault, degree of fracturing, and layering) are determined. The second group includes studies that are carried out in wells in order to determine the volume of potential production, that is, productivity studies. It should be noted that the quality of the results is influenced by a large number of factors that must be taken into account in the process in order to increase the degree of reliability of the information obtained about the reservoir system. Thus, this article provides an analysis and the degree of influence of one or another parameter on the reliability of well test results. Keywords: flow rate, test duration, well, reservoir properties, skin factor, permeability, bot-tomhole pressure.

Research on Fracturing Technology for Low Production and Low Efficiency Casing Damaged Wells

With the further development of Daqing Oilfield, the proportion of casing damaged wells is increasing day by day, because the casing damage location is mostly located in the upper part of the reservoir, the conventional technology can not carry out targeted fracturing construction,the low-yield and low-efficiency wells which limits the efficient development of the oil field. In order to satisfy the needs of subdivision and large-scale fracturing construction of low-yield and low-efficiency wells with casing damage, this paper studied the fracturing design principles, determined the optimal design theory of different types of wells, and can make effective fracturing schemes for different reservoirs and well conditions. At the same time, a kind of small diameter segmented fracturing tools have been developed, which can meet the fracturing operation of wells with diameter above 104mm, so that the number of fracturing segments and the scale of reconstruction are greatly higher than those of conventional technology. 30 wells have been tested in the field, and the effect of increasing oil and injection is obvious. The results show that this process can effectively improve the production status of casing damage, low production and low efficiency wells and increase the productivity of single wells.

Time-Lapse Pulsed-Neutron Logs for Carbon Capture and Sequestration: Practical Learnings and Key Insights

Pulsed-neutron logs are a staple of time-lapse monitoring programs for saline aquifer carbon capture and sequestration (CCS) projects and are unsurprisingly the most frequently run wireline logs in both injection and monitoring wells. While the emphasis imposed by government regulators and the focus of operators to date has been on the verification of CO2 containment, it is envisioned that a savvy interpretation of the multiple independent measurements should be able to unlock much greater value for the project than merely detecting the location of stored CO2. Recently introduced capabilities for novel measurements and improved environmental compensation should further increase the repeatability, interpretability, and value of these logs. We reviewed more than 30 time-lapse runs of pulsed-neutron logs acquired over a period of 15 years on three mature CCS projects using both previous- and new-generation pulsed-neutron tools, including measurements of formation sigma, hydrogen index, and fast neutron cross section. Special attention in processing is required when changes occur to the wellbore environment between runs, although this is mitigated by the improved environmental compensation scheme of the newer tool. We performed both standalone estimates of CO2 saturation from single-physics time-lapse measurements and simultaneous interpretation of multiple independent time-lapse measurements and studied the results side-by-side with openhole log interpretation, core analysis, and well test results from the evaluation phase. The apparent changes in saturation were framed within the context of the injection history and important events in the life of the wells. A first finding is that differences in apparent CO2 saturation between the various independent measurement physics of the pulsed-neutron tool are often reconcilable and may carry additional information about the state of the well or reservoir. With respect to verification of containment, depending on the well configuration, it may be possible to differentiate between CO2 in the formation and CO2 in the annulus. The interpreted CO2 saturation itself can have different significance depending on the timing of acquisition and the type of well. Measured at the right time, it is a direct in-situ measurement of formation CO2 storage efficiency. In other cases, the interpretation reveals formation dryout in the near-wellbore region of injection wells, a condition that may presage loss of injectivity. We now understand that it is important for operators to plan the timing and frequency of pulsed-neutron runs according to what they want to measure and not based solely on regulatory obligations. In a CCS project, time-lapse pulsed-neutron logs should be thought of as much more than simple indicators of the presence and migration of CO2. They give important information about migration pathways. They can also help to quantify essential uncertainties on reservoir performance that are difficult to ascertain during evaluation. For example, storage efficiency is difficult to quantify with openhole logs since the formation is initially at zero CO2 saturation. Yet it is one of the keys to determining the ultimate storage capacity of any reservoir. Time-lapse pulsed-neutron logs provide an abundance of information that, when properly history matched, can greatly improve our models of CCS reservoirs to better navigate both the economic and operational risks associated with these projects.

Research Status and Development Prospect of Wellbore Integrity in China

Summary As the exploration and development of oil and gas move into increasingly challenging locations and harsher environments, well integrity becomes more difficult to maintain. High temperatures, pressures, and corrosion can all contribute to wellbore integrity failure. Such failures can have significant financial and environmental consequences, including gas leakage and fluid spills. In this paper, we review the development and technical advancements of wellbore integrity research both in China and abroad and look forward to the development direction of wellbore integrity in China. We provide basic background knowledge for those interested in wellbore integrity and also share the progress and development direction of integrity research for wellbore integrity researchers. Through research and analysis, some conclusions can be drawn. Countries around the world are actively studying wellbore integrity and have developed a large number of standards, especially the United States and Norway, which have the most standards. The most common way to analyze wellbore integrity is to first divide the entire wellbore into different wellbore barrier units according to different standards, such as ISO 16530-1, and then study risk factors and integrity management measures in different units. Mainstream research is mostly carried out around the integrity of casing, cement, and tubing, and many achievements have been made, but the study of packer and downhole safety valve is still on the way. Wellbore integrity risk assessment aims to quantify potential risks and establish risk levels to support decision-making for on-site wellbore integrity control. This is achieved by identifying factors affecting wellbore integrity, establishing an evaluation index system and processing evaluation indicators to determine failure probability and impact consequences. The resulting risk value can be divided into different areas using the “as low as reasonably practicable principle” or a risk matrix graph. However, due to the complexity of the factors involved and the subjectivity of risk classification rules, there are still challenges in promoting the evaluation model and reducing errors in the evaluation results. China should actively promote interdisciplinary integration and respond to the call for “dual carbon goals” to break through the current bottleneck in wellbore integrity research. This can be achieved by promoting the development of quantitative wellbore integrity risk assessment methods, developing supporting evaluation software based on big data, and by tackling the integrity challenges faced by different types of wells and promoting the development of wellbore integrity discipline.

Assessment of water quality using multivariate statistics and geographical information systems (GIS) of Wadi Aldabab, Taiz, Yemen

The shortage of water resources in Yemen has an implication on the availability and supply of safe water in the country. This study assessed the water quality in Wadi Al-Dabab, Taiz, Yemen. Water samples were collected from the springs and different types of wells (tube, manual) with depths ranging from 9 to 500 m. Multivariate statistical analysis was performed on 15 water quality parameters (WQP) from 15 locations to investigate the significant WQP and the possibility of data reduction. The water quality index (WQI) approach was used to assess its suitability for drinking purposes. Four principal components were identified to be significant, which explained 86.2% of the overall variance while four varifactors (VF) explained 80% of the data variance. The findings showed the possibility of data reduction by 20%, which could assist in water quality monitoring at a reduced cost. The WQI map shows that the water quality is good in a limited area and poor to very poor in most of the study area. The findings are likely to assist in identifying the important WQP for the protection of the drinking water sources while the less important WQP can be excluded, which might reduce the cost of water quality monitoring. The proposed approach is likely to be a cost-effective approach for the economically weak and water-stressed countries, which can contribute positively for the sustainable water resource management in Yemen and other water-stressed regions.

Identification of Factors Influencing the Presence of Fecal Coliforms in Densely Populated Areas with Centralized Wastewater Treatment Systems

Introduction: Tegal Panggung is a high population density sub-district of 26,326 inhabitants/km2. Most residents utilize wells to meet their water demands, but fecal coliform bacteria were found in several wells at Tegal Panggung. This type of contamination source is typically from on-site wastewater treatments. However, wastewater from Tegal Panggung is treated at a centralized wastewater treatment plant. This study is aimed at identifying the factors leading to the presence of fecal coliform bacteria in Tegal Panggung. Methods: Factors reviewed in this study were the amount of waste, drainage, cattle pens, toilets, types of wells, and building density. Statistical methods and GIS were applied to determine the influence of the factors on the presence of fecal coliform and to map its distribution along with potential sources of pollution. The number of wells tested was 32, with a research period from September to October 2021. The statistical methods used are the Kolmogorov-Smirnov Normality Test, the Spearman Correlation Test, and the spatial analysis method, which was carried out using QGIS. The statistical tests were conducted to determine the correlation value between fecal coliform and pollutant. Results and Discussion: The study showed that only 40.62% met the standard requirements when there should be no fecal coliform contents in well water. Conclusion: Based on the Spearman Correlation Test, it can be deduced that the factors affecting the presence of fecal coliform within 10 meters radius are garbage and of 30 meters radius are toilets and building density.

THE MAIN PROBLEMS IN THE CEMENTING LONG EXTENDED REACH WELLS IN CUBA

Cuba advances in the development of drilling long extended reach wells (ERD). An extended range well is defined as one that has a true horizontal deviation-vertical depth (MD/TVD) ratio of more than 2.0. This relationship is an indication of the high complexity of conducting or constructing these types of wells: the higher the ratio, the more complex the well. It is important to note that this is only a basic indicator of the difficulty of drilling and completion of the well. Most of the recently developed wells of this type are in the north-west fields of Cuba, between the provinces of Havana and Matanzas. The True Vertical Depth (TVD) is 1,500 to 2,000 meters, and the horizontal displacement is up to 8,000 meters. However, experience has shown that the quality of the cementation of the extended reach wells in Cuba does not correspond to what is required. Among the most common problems affecting the cementation work of oil wells we can find the poor condition of the well (deviation, well stability, layer of cuts, etc.); poor condition of the mud (high gel stability, high circulation or filtration losses, high solids content, loss of circulating material, incompatibility between drilling fluid and cement); loss of circulation; abnormal pressures (abnormally low pressures, high pressures, etc.). One of the most complex problems to solve by well construction is poor centralization: cement is unevenly distributed throughout the cladding, leaving the cuttings in place. The paper reveals the main problems identified in the cementing long extended reach wells in Cuba and some technological proposals for their solution.

Substantiation of Drilling Parameters for Undermined Drainage Boreholes for Increasing Methane Production from Unconventional Coal-Gas Collectors

Decarbonization of the mining industry on the basis of closing the energy generation, on the basis of cogeneration of coal mine methane, and on the internal consumption of the mine is a promising direction in ensuring sustainable development. Known problems of deep underground mining do not allow for realizing the potential of man-made gas reservoirs due to the deterioration of the conditions of development of reserves of georesources. The aim of the work was to improve recommendations for the substantiation of drilling parameters for undermined drainage boreholes for increasing methane production from unconventional coal-gas collectors. The authors’ approach innovation lies in the possibility of using the established patterns of better natural stability of undermined boreholes to optimize them as spatial orientation parameters in an existing drilling passport for the improvement of methane extraction productivity. For this purpose, smoothing (LOESS) of the experimental data of two similar types of wells was used; then deterministic interpolation methods in combination with a three-dimensional representation of the response function in “gnuplot” were used. As a result, it was found that the increase in the inclination angle from 40° to 60° leads to a significant transformation of the model of the studied process, accompanied by a decline in the dynamics of methane emission and a decrease in the distance of the productive work zone of this type of well from 13 to 5 m before the roof landing, which then is replaced by a sharp increase in the productive work zone up to 35 m ahead of the longwall face. This allows under specific conditions for recommending increasing the productivity of methane capex from technogenic disturbed coal-gas reservoir replacement of wells with a smaller angle of rise to the transition to a more frequent grid of clusters from wells #4.

ANALYSIS OF EFFICIENCY OF HORIZONTAL WELLS WITH MULTI-STAGE HYDRAULIC FRACTURING ON THE EXAMPLE OF KONDINSKOYE FIELD

In the structure of potential oil reserves in Western Siberia, the share of hard-to-recover reserves (HRR) is growing. At the same time, a significant share of these reserves is concentrated in low-permeability reservoirs. Horizontal wells using multi-stage hydraulic fracturing are the basis of technological solutions used for cost-effective development of low-permeability reservoirs by Russian oil and gas producers [1-4]. Due to the high efficiency of the subsea development systems with MSHF, oil production from such facilities exceeds oil production from traditional reservoirs and accounts for more than 60 % of the total oil production of the Company's fields [5]. The following characteristics are identified as the key parameters of the horizontal section, the number of hydraulic fractures, as well as the specific weight of the injected proppant at the frac stage. The decisions approved as part of the design documents for the development of facilities with TPP indicate a tendency to increase the length of the horizontal hole and the number of frac operations with a decrease in the specific mass of proppant on the port. The article examines the impact of these characteristics on the technological efficiency of wells. The purpose of the work is to assess the feasibility of increasing the technological complexity of HW with multi-stage hydraulic fracturing of the MSHF formation in the form of increasing the number of stages and length of the horizontal hole, as well as the specific mass of proppantane in the example of the AS10/1 Kondinskoye field development target. Within the framework of the study, three types of HW with MSHF were identified, the technological effectiveness of which was assessed in two ways. The first method consisted in comparing the magnitudes of the dimensionless productivity coefficient Jd (d. units) of three different types of wells with a horizontal end in relation to directional wells (FWS with frac) of the environment. Taking into account the similarity of the geological conditions of the neighboring wells, this method made it possible to assess how effectively the completion of the horizontal wells under study was completed. The multiplicity assessment methodology was developed by RN-BashNIPIneft LLC [6]. The second method was to compare the ratio of dimensionless productivity factor to the specific weight of proppant Jd/Mpr _ specific of the identified types of HW with multi-stage hydraulic fracturing (MSHR). This approach made it possible to take into account the effective thickness and permeability of the formation in the well drilling zone, as well as the weight distribution of the injected proppant. The results showed that if the length of the horizontal hole is constant, an increase in the number of frac stages while reducing the proppant weight on the port is impractical. Confirmation was also obtained based on statistical data that there is a relationship between the cumulative fluid withdrawal and the weight of the injected proppant. It has been established that drilling HW with multi-stage hydraulic fracturing of the (MSHF) formation of the most common type (1000 m, 10 stages) is not optimal for the study target: for a length of 1000 m, the maximum number of stages should be limited to 7–8 units per well. Further monitoring and analysis of production wells with horizontal termination is recommended to collect more statistical data and compare them over time.

Hierarchical optimization of reservoir development strategy based on reinforcement learning

Production optimization is to increase the profitability of reservoir development by adjusting the type of wells and the rate of injection and production. Previous methods put both variables at the same level when optimizing and thus they change at the same frequency. However, these two variables belong to different scales, because well types require time-consuming and labor consuming operations such as borehole operations, while rate adjustment don't. Therefore, in this paper, a hierarchical optimization method is proposed to optimally control well types and corresponding rate in production sequence. Specifically, a hierarchical framework is first employed based on reinforcement learning method, with well types as high-level variables and quantities as low-level variables. Then, two hindsight mechanisms, named action hindsight and goal hindsight, are used to achieve stably joint optimization of two-level variables at different frequencies. Our findings from the case study reveal that our approach is highly practical, as it has successfully reduced operational costs by 90% and increased cumulative oil production by 18% within three years when compared to the single-level reinforcement method.

Multi-stage hydraulic fracturing technology in a well with horizontal working face

At present, hydraulic fracturing (HF) is still the most effective method of stimulating hydrocarbon flow and enhancing oil recovery in certain types of wells, particularly those with horizontal endings. In many regions, this is the only technology that enables development of fields with hard-to-recover reserves confined to low-permeability, poorly drained, heterogeneous and dissected reservoirs, which significantly increases hydrocarbon production and makes well construction economically viable. In this work, the authors have developed a new technology for interval hydraulic fracturing in a well with a horizontal target area, with the ability to inject fracturing fluid and hold excess pressure on either side of the fracturing unit by means of flap-type check valves. The fracturing is performed through a transport unit that runs directly through the casing and protects the plug from the abrasive effects of the gel-propellant mixture. After fracturing is complete, the transport unit is removed from the plug, and the rear cut-off valves are closed. No re-entry is possible after the adaptor has been removed from the well. For the next interval, the work cycle of plug, activation and fracturing is repeated using a new transport unit. For each repetition, the newly stimulated interval remains isolated until the fracturing operation is complete and all downstream plugs have been fractured. All installed plugs are drilled out before development. During all phases of the work, it is assumed that the well is prepared without the use of coiled tubing. The novelty and innovation lie in the technological solution of delivery to the target area and using easy-to-drill plugs to guarantee open interval separation and perform selective fracturing. Potential candidates are wells with 114 mm diameter casings with single- or multiple-acting fracturing sleeves to open-close after the horizontal part of the well has been prepared (the ‘equal-pass’ section requirement is for a 95 mm diameter bit). The proposed technical means and technology, in the opinion of the authors, will increase the efficiency of field development, reservoir conditions in which are characterized by low filtration parameters, high viscosity properties, etc. The authors do not think that the proposal will generally solve the problem of intensification of the inflow of reservoir fluid to the well and thereby increase oil recovery from the reservoir, but according to in their opinion, in some respects it will contribute to this. The final results will be obtained based on the results of extensive production tests.