Advanced drilling fluid technology in shale oil and gas wells

Arbaoui Abderrahmane Iyed, master's student

Ufa State Oil Technical University

Introduction

Hydrocarbons such as shale oil and gas are unconventional but have substantial reserves with the ability to be stored and produced through self-resorpeting, or being able to produce without artificial means, methods. Horizontal drilling and hydraulic fracturing technologies have changed North America's move away from being a net importer of oil to being a net exporter following the recent Shale Revolution. In addition to North America's shale oil resources, China has very large reserves of shale oil resources of about 270 million tons, focused primarily in the Junggar, Song Liao, and Bohai Bay basins, as well as potential shale gas reserves of approximately 105.7 trillion cubic meters within the Sichuan Basin. The following article will provide a review of different aspects of shale reservoirs as well as describe several technical challenges associated with drilling for hydrocarbons from these formations due to low porosity, low permeability, high clays, variations in lithology, and environmental issues attributable to drilling with oil-based (non-water-based) fluids. In particular, this article will examine some new technologies available to address problems associated with the drilling process in shale reservoirs, including advancements made to the technology of drilling and completing wells in shale reservoirs using both water-based and oil-based fluids, advances made in lost circulation control technologies, and establish a series of recommendations for future research aimed at further supporting the exploration of shale oil and gas in China.

1. Research Advances in Shale Oil and Gas Drilling Fluid Technology

1.1. Shale Oil and Gas Water-Based Drilling Fluid Technology

The main goal when managing water-based fluids, in all types of drilling operations, has always been to improve the performance of the fluids in the most important ways: sealing, inhibiting and lubricating these substances so that their performance is maximized throughout the entire drilling operation. To accomplish this, the use of advanced materials including nano-polymers, silica composites and graphene sheets is vital, as these materials have the ability to create a seal around the wellbore by filling in small cracks and pores and providing added structural support during the drilling process. The use of these materials also provides the operator with an effective means of preventing clay from swelling by providing an inhibitor via the addition of salts and organic amine-based products. The proactive nature of utilizing these advanced materials to maintain wellbore stability is most critical in order to maintain an enhanced and safe drilling operation, all the while maintaining the expected levels of performance required by an operator. Lastly, the growing use of very long horizontal wells has prompted a focus on developing new bioinspired lubricants that are designed to address the unique issues associated with high friction environments while increasing the overall reach of a given well. By utilizing cutting-edge lubricating products, operators can decrease the frictional resistance found in the drilling process, enhancing the total reach of the well while providing efficiencies and additional production capability within the context of maintaining wellbore stability.

1.2. Shale Oil and Gas Oil-Based Drilling Fluid Technology

Oil-based fluids are beneficial to the wellbore for improving the structural integrity of the wellbore and reducing costs and environmental impacts through reinforcement of the wellbore. Oil-based fluids are efficient in managing high temperature drills (drilling). As well, oil-based fluids that use nano-materials (nanoparticles) and graphene can effectively block the pores in shale rock fractures, increasing stability. Additionally, new technologies using new chemicals to clean and recycle the spent fluid are being developed which promote environmental sustainability and reduce the overall costs of the oil and gas industry. Also, the development of new technologies and methods to conserve oil are focused on reducing costs related to fluid use.

In addition to traditional oil-based fluids, the oil industry is moving towards an alternative battery of synthetics developed from either gas or plant source products. These synthetics not only provide a more environmentally-friendly option for drilling, but they also represent a more efficient way of conducting drilling operations. Additionally, synthetics help to reduce the overall carbon footprint related to oil exploration and production, while supporting worldwide sustainability initiatives.

Recognizing the difficulties associated with extremely high temperatures, research continues into the development of specialized advanced cooling systems to protect equipment from failure in these extreme environments. The advanced cooling systems are a breakthrough in wellbore engineering and allow for maximum operational efficiency and equipment life, even in extreme temperature environments. Utilizing advanced cooling systems, the oil and gas industry will be able to improve both resiliency and sustainability of operations in a variety of drilling applications.

1.3. Reservoir Protection Drilling Fluid Technology

To reduce damage to the rock that produces oil and gas, it is necessary to use fluid that contains no clay because clay has the ability to clog pores in rock. Clay-free fluids are created with the use of specially formulated chemicals instead of bentonite clay. Another way to reduce damage to producing rock is through under-balanced drilling, where the pressure exerted by the drilling fluid is slightly lower than that exerted by the confining pressures of the producing rock.

Interface modification is a significant technique used to reduce water entrapment in the pores of rock. In this case, certain chemical additives are applied to the surfaces of rock formations to create a surface modification of the rock that helps to minimize water entrapment. By utilizing all the aforementioned strategies together, the ultimate objectives are to reduce damage to producing rocks and to improve the production of oil and gas through enhanced drilling efficiency and success.

1.4. Lost Circulation Control Technology

This technologically advanced solution has been designed to meet the challenge of preventing the loss of drilling fluids into the earth's subsurface by minimizing risk of both environmental impacts and operational downtime. Bridging is the primary concept, where many different types of materials are combined to form a sturdy barrier that seals off very small cracks and crevices, creating an effective barrier against unwanted fluid losses. For more significant fractures or other large openings, gel-based systems that have very strong adhesive properties are used to seal these larger areas effectively. Other advanced technologies recently developed include the introduction of «smart» materials that are able to solidify in response to temperature changes or pressure changes in the wellbore. The ability of these materials to adapt to changing conditions, in theory, allows for optimum performance under varying drilling conditions. Additionally, composite technology has been developed to allow for the integration of multiple sealing systems to provide a comprehensive approach for dealing with severe drilling fluid losses. As a result, this new and innovative approach to the technology provides a way to protect both the integrity of the wellbore and the surrounding geologic formations from being damaged, and serves as an important tool in drilling operations by reducing the potential for leaks and negative environmental impacts while simultaneously improving drilling efficiency.

2. Problems in Shale Oil and Gas Drilling Fluid Technology

2.1. Problems in Shale Oil and Gas Water-Based Drilling Fluid Technology

Water Based Fluids are generally used in the process of drilling; however, there are some disadvantages associated with the use of Water Based Fluids. One of these disadvantages is the fact that clay particles can swell due to water absorption and cause instability while the drilling operation is being performed. In addition to clay particle absorption by water, the high temperature or saline conditions under which lubricants are used can adversely affect the performance of those lubricants, thereby increasing the potential for failure of a drilling operation. With the addition of carbon dioxide (CO₂) to the formation, Water Based Fluids may also become more susceptible to contamination, which can alter the characteristic properties of the fluid and reduce the efficiency of drilling operations. Engineers and Operators should take steps to mitigate these issues before they arise through the development of strategies to minimize the swelling of clay particles and enhance the performance of lubricants under challenging conditions, and prevent contamination of Water Based Fluids from carbon dioxide. Addressing these issues proactively will keep drilling operations operating efficiently and support successful drilling operations.

2.2. Problems in Shale Oil and Gas Oil-Based Drilling Fluid Technology

Oil based or petroleum-based fluids pose a significant number of threats to our environment because they are very costly to dispose of properly and they also have a lot of environmental risks attached to them. Petroleum based fluids are expensive not only to buy initially, but they require a lot of support over time by their users. Also, because of their inability to function well in extremely hot or cold operating conditions, there is a vast amount of sci-fi technology and research being done, but not all of this new cooling technology is cost-effective enough to be reasonably applied at an industrial level. Thus, to continue to develop sustainable options and increase operational efficiencies in the future, businesses must explore different ways to alleviate the issues associated with the use of oil based fluids. All industries should explore alternative types of fluids, as well as continue to research and develop new applications to aid in the increase of efficiency and reduce their impact on the environment with respect to their use of oil-based fluids. Through these efforts, businesses may be able to build an environmentally and economically sustainable future.

2.3. Problems in Shale Oil and Gas Reservoir Protection Drilling Fluid Technology

Drilling operations regularly experience difficulties related to differing laboratory test data and true, downhole conditions. One such difference arises with regard to non-clay-containing fluids that have a greatly reduced viscosity due to an increase in temperature over time. The cost and complexity of under-balanced drilling tools and equipment present another serious challenge for the industry. The uncertainty surrounding the usefulness of surface-modifying coatings and their expected longevity presents yet another challenge for the industry's systems, tools and equipment as a result of their importance in providing protection to the tools and equipment when used in extreme and/or tough environments where this type of equipment is employed. Together, all of these challenges create a highly uncertain and extremely dynamic environment in which drilling experts operate to be successful. Continued development through the continuing advances in new technologies and methods are an ongoing process in the drilling industry to support continued evolution in the development of drilling technology and methods that will ultimately reduce the impact of the above-described challenges on drilling operations. It is important for all drilling stakeholders/developers to work together to develop solutions for the above challenges to ensure continued successful operational performance of drills and associated equipment through greater efficiency and safety of drilling operations. Recognizing and addressing the major challenges described above will enable the drilling industry to implement more sustainable and effective practices to optimize overall performance and mitigate risk in the ever-changing world of drilling activities.

2.4. Problems in Shale Oil and Gas Lost Circulation Control Technology

The ability to find and quantify where and how much fluid has been lost is an ongoing major challenge in the oil and gas business. Many types of fluid loss can occur due to different events; therefore, each kind needs a different containment action taken. This is compounded by the added difficulties of dealing with oil and gas that have been produced from very high temperature, very high-pressure wells. In extremely high-pressure/high-temperature downhole conditions, most of the traditional sealing materials lose integrity and break down much more quickly, which requires operators to constantly check the integrity of the material they are using or replace it, making it very difficult for operators to manage their fluid losses effectively and efficiently, while at the same time dealing with the challenges presented by the downhole environment and the current sealing technologies' limitations. Despite continuous research and development efforts to improve the performance of sealing materials, the oil and gas business has not yet identified a single sealing solution that can solve the entire spectrum of fluid loss challenges. Because of this, the oil and gas industry is continuing to deal with uncertainties regarding operations and financial risk caused by fluid losses, which indicates that new innovative methods and advancements in technology are desperately needed in this critical aspect of well integrity management.3. Prospects for Shale Oil and Gas Drilling Fluid Technology

3.1. Prospects for Water-Based Drilling Fluid Technology

The evolution of any Industrial lubricant through the development of Nanotechnology to enhance lubricant performance requires the combination of Nano-Plugging Technology with Chemical Inhibition techniques into one Organic Compound for optimum lubricant advantages. This will create Smart Lubricants, which will increase the performance level of lubricants by improving Thermal Stability, especially in high-temperature environment applications where traditional industrial lubricants deteriorate quickly. Furthermore, The Smart Lubricants will provide a method of increasing the resistance of the lubricant to the effects of gas contamination (e.g., CO₂) through the creation of Innovative Formulations that will mitigate the degradation effects of gas contamination on lubricants and increase the longevity and reliability of lubricants in extreme operating conditions. Consequently, the technological advancement of lubrication systems focuses on a Holistic Approach that incorporates both Nanotechnology and Chemical Engineering Principles, thus providing industries with the opportunity to maximize the Efficiency and Productivity of their Operations.

3.2. Prospects for Oil-Based Drilling Fluid Technology

The objectives include the enhancement of new emulsifiers that will enable the quality production of low oil ratio fluids in a low-cost manner, formulation of eco-friendly products using plant-derived oils, development of higher temperature resistant emulsifiers, and improved processing/processing systems for enhanced efficiency/economy of coolants. Our strategic priority reflects our dedication to advancing chemical engineering and the implementation of sustainability in our industry while simultaneously supporting innovation and minimizing our environmental impact. In addition, we will strive to meet our customers' and stakeholders' changing marketplace demands by investing in collaborative efforts; through the use of collaboration, related research efforts, and continuous improvement initiatives, we will strive to achieve operational excellence and product quality and support growth and prosperity in the evolving environment of emulsifier technology.

3.3. Prospects for Reservoir Protection Drilling Fluid Technology

Research and design of a superior damage prediction system should be the focus of future developments within the industry, using cutting-edge artificial intelligence technology to develop faster and more efficient real-time systems for predicting failure due to damage. In addition, there is an urgent need to increase research into high-temperature additives that will improve the performance and longevity of industrial processes by utilizing superior materials at elevated temperatures. Upgrading the intelligence and integration of existing under-balanced pressure control systems to increase the efficiency of their operations while maintaining the highest safety standards in the most challenging environments will also be necessary to meet these challenges. Finally, there will be a need for innovative research to improve the long-term stability of protective membranes used on the surface of rock structures to maximize the life of these coatings and ensure their reliability. Through these research and development activities, the sector will enhance its capabilities and technological developments to adapt to the innovative solutions and demands of the sector in the future.

3.4. Prospects for Lost Circulation Control Technology

To advance effectively, the development and implementation of next-generation intelligent systems for providing real-time diagnostic solutions is required advance effectively, the development and implementation of next-generation intelligent systems for providing real-time diagnostic solutions is required. Additionally, resources should be allocated to the research and development of innovative smart matter.

4. Conclusions

Challenges exist for shale gas production, including issues with well integrity and the potential for damage to the reservoir and loss of fluid. The advances made through improved technology in the development of drilling fluids have provided some improvements, but productivity and cost continue to pose significant obstacles to the shale gas industry. Drilling fluid technology needs to be better developed to optimise performance, meet regulatory requirements and be economically viable. Developing high performance, intelligent and eco-friendly drilling fluid will improve operational efficiencies, reduce adverse environmental effects and create the basis for sustainable, profitable shale gas production in the future. Ultimately, the shale gas industry needs to develop a balance between drilling technologies, environmental considerations and productive efficiencies.

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