LEGAL ISSUES RELATING TO UNDERGROUND GAS STORAGE

In response to Governor Brown’s January 2016 state of emergency proclamation regarding the Aliso Canyon gas leak, SB 826 (Leno, 2016) requested that the California Council on Science and Technology (CCST) provide the State with up-to-date information on all currently operating underground natural gas storage fields in California. CCST was instructed to provide an independent technical assessment answering three key questions about: The risks California’s underground gas storage facilities pose to health, safety, environment, and infrastructure; Whether California needs underground gas storage to provide for energy reliability through 2020; and How implementation of California’s climate policies changes the future need for underground gas storage. From a statewide field of leading energy researchers, CCST selected Jens T. Birkholzer, PhD, and Jane C.S. Long, PhD, to serve as co-chairs of the 12-member CCST Report Steering Committee – which supervised 21 Report Authors with expertise spanning hydrogeology and reservoir engineering, risk assessment, public and occupational health, greenhouse gas (GHG) emissions, and energy analysis and economics. Each report chapter was subject to a peer review process by independent experts, while another independent expert served as Report Monitor to oversee the process, ensuring that peer review comments were sufficiently addressed in the final report. An additional Oversight Committee reviewed the entire process, including conflict-of-interest declarations. The report’s findings and conclusions are based on a review of published literature and official and voluntary databases, which the Report Authors compiled between January through September 2017, and delivered to the California Public Utilities Commission in January 2018. Key findings and conclusions include: Safety: The risks associated with underground storage (UGS) facilities can be managed, and, with appropriate regulation and safety management, may become comparable to risks in other types of energy facilities found acceptable in California, such as oil refineries and natural gas power plants. At each UGS facility, the State should ensure timely and thorough implementation of the new regulations coming into force in 2018 set by the California Department of Conservation’s Division of Oil, Gas, and Geothermal Resources (DOGGR). Those regulations emphasize new and safer well completions, risk and safety management plans, and requirements for well integrity testing and monitoring. The report recommends that the State go further and require more quantitative risk assessment activities, including consideration of human and organizational factors affecting risk. The State should also implement an independent and mandatory review program to evaluate the effectiveness of these new regulations and the rigor of their application in practice, with opportunity for public comment and public dissemination of the review results. Facility-by-Facility Evaluation: Any industrial operation involves some risk to health, safety, and environment. This report assessed various risk-related characteristics across UGS facilities in California, and found a small list of facilities had relatively higher potential risk compared to others. Reliability of Natural Gas Supply: California’s energy system currently requires natural gas and UGS facilities to run reliably, primarily because many residential and commercial buildings in California rely on natural gas for heating during the winter, and because natural gas provides electricity when solar and wind power are not available. The peak demand for natural gas during the winter currently exceeds the ability of pipelines to bring natural gas into the State of California, so natural gas must be stored during periods of low demand in order to have it available to meet peak demand. Near-Term Alternatives to UGS: Closing any or all UGS facilities in the near term would involve replacing UGS facilities with new pipelines or natural gas storage capacity, and require very large investments. Such new natural-gas-related infrastructure would bring its own risks and would further obligate the State to the use of natural gas for decades. The risks, costs, and benefits associated with alternatives to UGS storage should be evaluated accordingly. Long-Term Need for Underground Gas Storage: California’s climate policies in future decades could still necessitate the continued use of natural gas. Also, energy systems that meet the climate goals may require underground storage of natural gas, biogas, or hydrogen, as well as sequestration of carbon dioxide. The State should develop a more complete and integrated plan to understand how the role of natural gas might evolve; assess possible energy portfolios that both meet GHG emission constraints and achieve energy reliability; and consider the potential need for UGS facilities in the future.

The objective of this article is the analysys of methods for preventing and eliminating hydrates formations, classifying them and choosing the best ones for use in underground gas storage facilities. Comprehensive measures for the stable operation of gas storage facilities in the presence of conditions for the occurrence of hydrates formations were developed. Zones, being potentially prone to the hydrates formation during the gas storage facilities operation were identified. The operational parameters of gas storage wells during gas withdrawal are analyzed. The identified wells were operated under difficult conditions due to the deposition of hydrates on the wellheads, in flowlines and process equipment of gas storage facilities. The places of the highest hydrates accumulation on underground gas storages were determined: from the bottomhole of wells to the gas purification unit of the gas gathering station. Hydrate-prone zones were identified by computational fluid dynamic (CFD) modeling at the location of regulating choke installations in underground gas storage facilities. The zones of the greatest hydrates accumulation on underground gas storages were determined: from the bottomhole of wells to the gas purification unit of the gas gathering station. The analysis of the methods used in gas storage facilities of Ukraine to prevent and eliminate hydrates formation was out. A set of measures was proposed to prevent the hydrates formation in storage facilities to ensure their stable operation. Based on the Euler approach (Mixture model) by CFD modeling, zones prone to hydrates formation were determined at the installation site of regulating chokes in underground gas storages. The influence of the degree of fittings opening on the location of potential zones prone to hydrates formation was estimated. The gas-dynamic processes in the internal cavity of the gas pipeline at the installation site of the control fittings were studied and their influence on the distribution of bulk particles of the gaseous and liquid phases was established. Based on the studies performed, it was recommended to change periodically the mode of well operation for a certain time by opening or closing the regulating choke under favorable conditions for the formation of hydrates, especially at low ambient temperatures. The obtained results of experimental studies and calculations showed that in order to solve the problem of hydrates formation at gas storage facilities, it is advisable to use diverse measures through the introduction of modern intelligent systems for monitoring and controlling the technological process. Further refinement of the algorithm of the proposed monitoring and control system with its approbation in production was provided. The results of the experimental studies and CFD modeling carried out allowed providing a more reasonable approach to the application of various available methods and measures to prevent hydrates formation in underground gas storage facilities. This approach made it possible to develop new effective ways and measures to prevent such complication. Based on the conducted experimental studies and modeling, the major zones prone to hydrates formation in underground gas storages were determined. The developed measures will allow timely detection and prevention of hydrates formation at gas storage facilities are original.

The EU Directives implementing the climate and energy package will result in the increased demand for natural gas in all EU countries, especially in Poland, whose energy management is coal-based. In the following decades we will observe the substantial increase in demand for natural gas as an energy carrier in power and heating sectors. Another factor, which will contribute to the increase in gas consumption, is the expansion of gas transmission and distribution network. In order to secure natural gas supply for the customers in is necessary to ensure the proper gas storage capacity, expand the existing underground gas storage facilities (UGS) and build new ones. Currently used Polish underground natural gas storage facilities allow storing 1.6 billion m3. Taking into consideration the expansion of investments in underground natural gas storage facilities and the projected increase in demand for natural gas, it is justified to build the new large salt cavern underground gas storage facility in Poland.

The article analyzes the data on the creation of North Caucasus underground gas storage facilities (UGS) in1960-1971 and the injection and production of gas into storage facilities during exploration and industrial operation.The followings have been obtained as a result of the analysis. Increased gas injection and extraction from gas storagefacilities in the former USSR; change in the absolute value of gas over time, while it is pumping into storage, takingout and its rising; a decrease in the volume ratio of gas injection and extraction over time. Compression of water withgas is not very large. Therefore, it is hardened as follows. Under formation conditions, gas has a lower density thanwater, i.e. it is light and its viscosity is less than water, gas has a large mobility. In underground gas storages (UGS),gas is divided into active and buffer. The part of the gas that is extracted from the storage is called the active part(when the demand for gas decreases in the summer). Buffer gas refers to the part that is constantly in undergroundgas storage (UGS). It provides pressure in the reservoir and is sufficient to supply active gas to the production wells.The maximum and minimum pressures are obtained in underground gas storages (UGS-s) where the share of buffergas is very high. The volume of active and buffer gas in underground gas storages (UGS) depends on its geometricdimensions, shape, depth of deposition, porosity, rock permeability, minimum and maximum pressure in the annulus,gas injection and extraction technologies.

Underground gas storage as a promising natural methane bioreactor and reservoir?

Nigeria is the 2nd biggest natural gas producer in Africa, with much of it exported as LNG, some re-injected while a small fraction serves the domestic market. The volume supplied to the domestic market plays an outsized role in the energy mix and economy of Nigeria with over 90% supplied to thermal power plants and industrial clusters. As huge upstream gas projects continue to take Final Investment Decision, pipeline takeaway capacity grows and demand increases, the dependence on natural gas and preponderance in the energy mix will likely persist. Natural gas is the present and future of Nigeria's energy needs. The domestic gas industry is evolving but has been fraught with challenges. Oil and gas infrastructure are often disrupted and production shut-in, mostly triggered by infrastructure unavailablity, environmental concerns and prioritisation of hydro power generation during River Niger's white and black floods, all of which come at a cost to upstream producers. Gas producers are often compelled to curtail production of gas plants (associated and non-associated) to avoid environmental disasters and prohibitive gas flare penalties. Can underground gas storage (UGS) be an opportunity for gas producers to guarantee continued operations during disruptions and provide buffer for national strategic benefits? This paper seeks to explore the potential technical and economic dynamics of underground natural gas storage in Nigeria in the context of extant technical regulations, seasonal demand variations, gas flare penalties and local operating environment. The paper presents types of underground storages and recommends the most suitable, considers options for optimal location of UGS in Nigeria and undertakes an economic evaluation of a UGS project. The findings are further presented alongside the critical technical, regulatory and fiscal factors that may facilitate future investments and growth of underground gas storage in Nigeria.

PurposeThe purpose of this study is to investigate the impact of the construction and operation of underground gas storage (UGS) facilities, under the prism of the recent rise in energy prices. The focus is on developing energy markets interconnected with gas producers through pipelines and has access to liquefied natural gas (LNG) facilities in parallel.Design/methodology/approachThrough a focal market in Europe, the authors estimate the economic value for both stakeholders and consumers by introducing a methodology, appropriately adjusted to the specificities of the domestic energy market. The Transmission System Operator, the Energy Market Regulator, the Energy Exchange and Eurostat are the main data sources for our calculations and conclusions.FindingsThe authors investigate the perspectives of UGS facilities, identifying financial challenges considering specific energy market conditions which are barriers to new storage facilities. Nevertheless, the energy price rocketing coupled with the security of gas supply issues, which arose in autumn 2021 and were continuing in 2022 due to the Russia–Ukraine crisis, highlight that gas storage remains, at least for the midterm, at the core of European priorities.Originality/valueThe paper emphasizes on developing markets toward green transition, proposing tangible policy recommendations regarding gas storage. A new methodological approach is proposed, appropriate to quantify the economic value of UGSs in such markets. Last, a mix of energy policy options is suggested which include regulatory reforms, support schemes and new energy infrastructures that could make the gas storage investments economically viable.

Summary Underground storage of natural gas is a mature industry vital to a gas delivery system. It developed as a subdiscipline of gas technology with certain additions. This overview treats containment of gas without migration, monitoring, inventory verification, retention of well deliverability, practice and advantages of delta pressure, aquifer behavior, and compressed air storage. Introduction Underground storage is the process which effectively balances a variable demand market with a nearly constant supply of energy provided by the pipeline system. Storage reservoirs are the warehouses to give a ready supply of gas that can serve a market with high peak demands in cold weather. The natural gas simply is injected into-underground storage reservoirs when market demand falls below the supply available from the pipeline. It is withdrawn from the storage environment to supplement the steady supply from the pipeline when the demand exceeds the supply. Through the years, underground storage has become a mature industry.For northern climates, storage gas represents about 20% of the annual sales - on a cold day, storage gas may reach 50 to 70% of gas sold. With a superb record of providing continuous fuel service to residences, hospitals, and commercial buildings, underground gas storage has been a vital part of natural gas distribution systems. Historically, underground storage (which was practiced first in 1915) experienced a remarkable growth starting in 1950, resulting in nearly 7.5 Tcf (212 × 10 m) of storage in more than 399 pools in 26 states by 1979. Some gas storage literature covering developments over the years are listed in Refs. 1 through 12. Current Status The underground storage committee of the American Gas Assn. (AGA) compiles annual statistics for the industry. Fig. 1 shows the growth of the total quantity of gas in storage reservoirs and the quantity of working gas withdrawn in a given year. Table 1 gives AGA statistics on the reservoirs, facilities, and magnitude of certain parameters. Fig. 2 is the AGA map showing the location of storage projects. Although the annual volumes of gas distributed currently are not increasing and may even decrease in some areas as a result of conservation, the change toward a larger fraction of the gas going to spaceheating has a tendency to increase the need for storage.When the expensive synthesis gas from coal and pipeline-accessible gas from Alaska and Mexico arrive in the market, storage will become increasingly important. In the case of synthetic natural gas (SNG), storage will permit matching a variable supply to the variable demand of the markets.A brief history of the technical developments during the past 40 years is given next. Early field design procedures were adapted from natural gas production technology. A series of studies conducted during the 1950's resulted in (1) practices for more efficient use of the storage reservoir, (2) assurance that injected gas remained in the reservoir, and (3) ways to handle new problems as they arose. Some of our more recent activities are described in the following sections. Development of Underground Storage Historical records show that gas storage began by allowing depleted gas reservoirs produced in the winter to be recharged in summer by pipeline gas. As the intercontinental pipeline systems spread rapidly in the postwar period, reservoirs were selected and refurbished for full use as underground storage reservoirs. JPT P. 943^

The storage of natural gas in geological structures such as depleted fields, aquifers and salt caverns plays an important role in a gas supply system as it balances the fluctuation of gas demand and price. Hydraulic loss due to fluid flow through gas storage production equipment and an interfering effect from nonequal productivity index of storage wells may have an important influence on gas storage performance. An integrated mathematical model is developed based on underground gas storage facility production data. Using this model, the hydraulic loss is determined. A real test case that consists of a gas storage reservoir linked to the surface facility is analysed. The mathematical model uses an experimentally determined pressure drop coefficient in chokes. The base case scenario created using real gas storage facility data enables the achievement of a good history match with the given parameters of the gas storage reservoir. Using the history match simulation case as an initial scenario (a base case), two different scenarios are created to determine the injection and withdrawal performance of the gas storage field. The results indicate that the pressure drop in chokes, when fully open as a constraints in an underground gas storage facility, has a significant impact on gas storage operations and deliverability.

6 - Underground natural gas storage

Evaluation of underground gas storage capacity in the depleted gas reservoir with water evaporation and salt precipitation

The article is devoted to the study of gas turbine compressor units and, on the basis of this, the determination of technological, parametric and specific criteria and features of the use of gas turbine centrifugal compressor units in gas transmission systems and underground gas reservoirs. For this purpose, the advantages and disadvantages of gas turbine compressor units are analyzed. Comparative information is provided on the use of centrifugal, piston and screw compressors, which are often used in the oil and gas industry. The influence of the supply limit and supply volume, production time, and maintenance procedures on the choice of compressor type is shown. shown. A number of gas turbine compressor stations currently operating in Azerbaijan have been reported. The problems of gas lift operation of wells and the use of gas turbine centrifugal compressor devices in gas transmission systems and underground gas storage facilities have been studied from the point of view of technological, parametric and specific criteria, the unique characteristics of each system have been determined, and the unique characteristics of each system have been determined. Recommendations for pre-design studies have been developed for the purpose of using gas turbine centrifugal compressor devices in various systems. Keywords: gas turbine, compressor, gas lift system, gas transport, underground gas storage.

Main objective of this study is dealing with a real case study of an Iranian gas condensate reservoir for the purpose of underground gas storage. Doing such a study in this reservoir will aid developing this technology and also demonstrates new concept of underground gas storage in partially depleted gas reservoirs. After gathering some data about the reservoir and preparing a geological model for the field, a simulation plan considered for this field. Static model converted to a dynamic one by assigning reservoir fluid data. Finally, compositional model of the reservoir prepared and verified to be accurate through a history matching process. After being sure about accuracy of the model and validating it, different scenarios for underground gas storage developed. Depletion and gas storage scenarios made for the field and results obtained. Gas storage in partially depleted gas reservoir considered in scenarios for developing this field too. After comparing different scenarios some practical results achieved and best scenario for developing this field chosen. Introduction An underground gas storage system can be defined as a combination of a constant supply with a variable demand for economic advantages[1]. In other words, it helps to combine low-demand summer season and high-demand winter season. The whole process is injecting natural gas or rarely other gases into subsurface reservoirs in the periods that demands fall bellow the gas supply. When demands exceed the supply, the gas will be withdrawn from the reservoir. Fluctuating demands due to temperature and climate make it an economic process that is necessary in many cases for efficient use of the pipelines. It also helps to have an effective delivery during peak demand seasons. This process can also help producing oil or condensate and can be considered as an IOR method too. By increasing demand of gas in many areas of the world, developing storage plans and effective use of existing storage sources is a priority for engineering and economic advantages. Figure 1 illustrates natural gas supply and demand relation and clarifies importance of having some gas stored in low demand periods in order to use in high demand periods. Figure 1- Natural gas supply and demand. (Source from [2]) (Available in full paper) Depleted gas reservoirs called to be the best choice of underground gas storage and almost all early projects were developed in depleted gas reservoirs. There are of course other types of underground gas storage that are storing gas in aquifers and in caverns and salt structures. Peak load natural gas consumption has become a problem in big cities in Iran, especially in Capital. Underground gas storage technology seems to be a helpful key to overcome this trouble. Reservoir Summary A gas condensate reservoir is chosen for the purpose of underground gas storage that is located in central Iran. This field discovered in 1955 and its production started in 1959. It has a structure that is a northwest-southeast trending anticline approximately 25 kilometers long and about five kilometers wide. The structure is investigated by surface and seismic surveys and eight wells drilled on the field.

HTB underground gas storage (UGS) is a gas storage facility rebuilt from a depleted gas reservoir. It is located in Changji Xinjiang Province, in northwestern China. With designed working gas volume 45×108m3 and peak working rate 27×106m3 per day, HTB UGS is the biggest UGS constructed in China. Since commissioning in June 2013, HTB UGS has been injecting gas 113.8×108m3, and withdrawing gas 78.2×108m3 until now. In order to analyze its production performance after 7 years operations, we figured out a systematic analysis method. First of all, we built a production database for HTB UGS, collecting daily injection-production data, tubing pressure, and kinds of testing data of the storage. Also, we built a database for all 30 injection-production wells recording their geologic information, drilling information, gas injection-production information, etc. Based on detailed data, we analyzed the operating characteristics of the HTB UGS from 6 aspects: injection-production gas volume, liquid production volume, operating pressure, reservoir connectivity laterally and vertically, sealing of the trap and well-patten spacing. It shows that 1) gas injection and production volume of the storage increases year by year, accounting for 20% working gas volume of UGS in China. 2) Oil and water production are relatively low. The gas is becoming more and more like dry gas. 3) The operating pressure during gas injection almost reaches maximum allowable storage pressure (34 MPa); while during gas withdrawal it reaches 26 MPa, far above the minimum storage pressure (18 MPa). 4) Overall reservoir connectivity is good in the lateral direction and it is disconnected in the vertical direction between E1-2z21 and E1-2z22. 5) The storage is well-sealed and there is no gas leakage. 6) The well-patten covers 80% of the gas storage. To sum up, HTB UGS works well generally from 2013 to 2020, playing an increasingly significant role in summer and winter seasons in China. However, in order to guarantee gas withdrawal in limited time (120 days in winter time in China), well pattern infilling is still needed in layer E1-2z22. The construction of UGS in China started in 1999. At present, 27 gas storage facilities have been built and it is planned to build another 23 to generate more than 400×108m3 working gas volume by the end of 2030. However, a systematic performance analysis method for UGS has not been applied. This paper will offer the reference for production performance analysis of UGS.

As the UK advances toward net zero, it faces the critical challenge of balancing the competing demands for secure, affordable, and low-carbon energy. Yet, with only 12 days of gas storage capacity - compared to 90 in Germany, more than 100 in France, 123 in the Netherlands, and up to 150 days in Italy - the UK remains exposed to supply disruptions and price volatility. The Bains project, a depleted natural gas reservoir in the East Irish Sea Basin, is being developed into an underground natural gas storage (UGS) facility. Once operational, it will increase the UK's gas storage capacity by up to 50%, significantly strengthening energy security. Looking ahead, the project also aligns with the UK's decarbonisation goals by offering the potential for future large-scale hydrogen storage, a critical enabler of the hydrogen economy. A key challenge in developing such infrastru