In-situ hydrogen wettability characterisation for Underground Hydrogen Storage

Hydrogen storage in subsurface aquifers or depleted gas reservoirs represents a viable seasonal and/or long-term energy storage solution. However, currently, there is a scarcity of subsurface petrophysical data for the hydrogen system, limiting modelling work and industrial rollout. In this work, we address the knowledge gap by determining the wettability and Interfacial Tension (IFT) of the hydrogen-brine-quartz system using a multi-modal, in-situ approach. We utilise the captive bubble, pendant drop and in-situ 3D micro-Computed Tomography (CT) methods to rigorously characterise a hydrogen-brine-Bentheimer rock system, applicable to high quartz sandstone storage systems generally. The captive bubble method determined the effective contact angle ranged between 29°-39° for pressures 6.89-20.68MPa and salinities from distilled water to 5000ppm NaCl brine. In-situ methods confirmed the water-wet system with the mean of the macroscopic and apparent contact angle distributions being 39.77° and 59.75° respectively. Further confirmation of the water-wet system was provided by curvature analysis of fluid clusters. The pendant drop method determined that IFT decreased with increasing pressure in distilled water from 72.45 mN/m at 6.89MPa to 69.43 mN/m at 20.68MPa. No correlation was found between IFT and salinity for the 1000ppm and 5000ppm brines. Our fundamental studies provide insights into the physics of hydrogen wetting in multiphase environments of subsurface reservoirs. With this, we can make informed estimates of relative permeability and capillary pressure for the hydrogen-brine system to model the storage capacity and withdrawal rate of hydrogen in target reservoirs.

FEP Based Model Development for Assessing Well Integrity Risk Related to CO2 Storage in Central Luconia Gas Fields in Sarawak

Underground storage of CO2 in depleted gas reservoirs is a greenhouse gas reduction technique that significantly reduces CO2 released into the atmosphere. Three major depleted gas reservoirs in Central Luconia gas field, located offshore Sarawak, possess good geological characteristics needed to ensure long-term security for CO2 stored deep underground. Long-term integrity of all the wells drilled in these gas fields must be ensured in order to successfully keep the CO2 stored for decades/centuries into the future. Well integrity is often defined as the ability to contain fluids without significant leakage through the project lifecycle. In order to analyze the risk associated with all 38 drilled wells, that includes 11 plugged and abandoned (P&A) wells and 27 active wells, probabilistic risk assessment approach has been developed. This approach uses various leakage scenarios, that includes features, events, and processes (FEP). A P&A well in a depleted reservoir is a very complex system in order to assess the loss of containment as several scenarios and parameters associated to those scenarios are difficult to estimate. Based on the available data of P&A wells, a well has been selected for this study. All the barriers in the example well have been identified and properties associated with those barriers are defined in order to estimate the possible leakage pathways through the identified barriers within that well. Detailed mathematical models are provided for estimating CO2 leakage from reservoir to the surface through all possible leakage pathways. Sensitivity analysis has been carried out for critical parameters such as cement permeability, and length of cement plug, in order to assess the containment ability of that well and understand its impact on overall well integrity. Sensitivity analysis shows that permeability of the cement in the annulus, and length of cement plug in the wellbore along with pressure differential can be used as critical set of parameters to assess the risk associated with all wells in these three fields. Well integrity is defined as the ability of the composite system (cemented casings string) in the well to contain fluids without significant leakage from underground reservoir up to surface. It has been recognized as a key performance factor determining the viability of any CCS project. This is the first attempt in assessing Well Integrity risk related to CO2 storage in Central Luconia Gas Fields in Sarawak. The wells have been looked individually in order to make sure that integrity is maintained, and CO2 is contained underground for years to come.

Zmiany parametrów mieszaniny gazu ziemnego z wodorem w trakcie eksploatacji komory magazynowej w kawernie solnej

Underground gas stores are built in depleted gas reservoirs or in salt domes or salt caverns. In the case of salt caverns, the store space for gas is created by leaching the salt using water. Gas stores in salt caverns are capable to provide the distribution network with large volumes of gas in a short time and cover the peak demand for gas. The salt caverns are also capable to store large volumes of gas in case when there is too much gas on a market. Generally, the salt caverns are used to mitigate the fluctuation of gas demand, specifically during winter. The gas provided to the distribution network must satisfy the requirements regarding its heating value, calorific value, volumetric content of hydrogen and the Wobbe number. Large hydrogen content reduces the calorific value as well as the heating value of gas and thus its content must be regulated to keep these values at the acceptable level. One should also remember that every portion of gas which was used to create the gas/hydrogen mixture may have different parameters (heating value and calorific value) because it may come from different sources. The conclusion is that the hydrogen content and the heating value must be known at every moment of gas store exploitation. The paper presents an algorithm and a computer program which may be used to calculate the hydrogen content (volumetric percentage), heating value and calorific value (plus the Wobbe number) of gas collected from the salt cavern at every moment of cavern exploitation. The possibility of the presence of non-flammable components in the mixture and their effect on the heat of combustion / calorific value were considered. An exemplary calculation is provided.

Magazynowanie wodoru w obiektach geologicznych

Hydrogen economy became one of the main directions in EU’s Green Deal for making Europe climate neutral in 2050. Hydrogen will be produced with the use of renewable energy sources or it will be obtained from coking plants and chemical companies. It will be applied as ecological fuel for cars and as a mix with methane in gas distribution networks. Works connected with all aspects of hydrogen infrastructure are conducted in Poland. The key problem in creating a hydrogen system is hydrogen storage. They ought to be underground (RES) because of their potential volume. Three types of underground storages are taken into account. There are salt caverns, exploited gas reservoirs and aquifers. Salt caverns were built in Poland and now they are fully operational methane storages. Oli and Gas Institute – National Research Institute has been collaborating with the Polish Oil and Gas Company since 1998. Salt cavern storage exists and is used as methane storages. Now it is possible to use them as methane-hydrogen mixtures storages with full control of all operational parameters (appropriate algorithms are established). Extensive study works were carried out in relation to depleted gas reservoirs/aquifers: from laboratory investigations to numerical modelling. The consortium with Silesian University of Technology was created, capable of carrying out all possible projects in this field. The consortium is already able to undertake the project of adapting the depleted field to a methane-hydrogen storage or, depending on the needs, to a hydrogen storage. All types of investigations of reservoir rocks and reservoir fluids will be taken into consideration.

An Innovative Well Intervention for Production Optimization in Depleted Gas Reservoirs Thru Coil Tubing

Coil Tubing operated in NL wells, South Sumatera because of depleted reservoir pressure. Objective of coiled tubing operation are sand clean-out and acid stimulation to restore well productivity. Previously in NL wells has used a snubbing unit in intervention well but the results were not good. Formation damage was suspected due to packer fluid introduced into formation during snubbing job. Production optimization in brownfield is required to extend the economic producing life of the field using cost-effective and low-risk technologies. Well stimulation is generally proposed to enhance well productivity by acidizing treatment. Acidizing in sandstone applied in Medco to improve well productivity. But loss problem got in conventional rig operation during killing well in low reservoir gas well. Coiled tubing (CTU) can solve the problem and can operate without killing the well. Recipe acid HCl 15% get optimum in solubility test around 28-31%. Coiled Tubing Operation applied pulsonic method to get optimum result. After CTU Job (clean sand out & acidizing), well productivity improved refer to gas rate and flowing well-head pressure (FWHP) monitoring. Initial gas gain was more than 2.5 MMSCFD from 2 wells (NL-X1 and NL-X2) that were treated with CTU acid stimulation. Gas cumulative is around 176 MMSCF (3 months production) and still counting. Further evaluation will be conducted by performing complete well test (transient analysis). As conclusion, coiled tubing operation has proven to become effective well intervention in depleted gas wells to improve production optimization and open the opportunity to unlock potential in other wells which experiencing similar challenges. This paper shares case study, how to develop acid stimulation strategy covering guideline in acid selection and deploy acid without killing well in South Sumatra.

Approbation of the technology for displacing residual gas with nitrogen for the conditions of a depleted gas reservoir in the VS-9 horizon of the Lyubeshivske gas field

Most natural gas reservoirs of Ukraine are depleted to some extent; still they contain significant tail gas reserves. A promising direction for increasing gas recovery from depleted gas reservoirs is the displacement of tail gas from the porous medium with nitrogen which is easily accessible and does not cause corrosion of the down-hole equipment. This article characterizes the technologies for increasing gas recovery from depleted gas reser-voirs by injecting nitrogen into them. The technology of replacing tail gas with nitrogen is tested on the example of the depleted reservoir of ND-9 horizon of Lyubeshivskyy gas field, the productive deposits of which are composed mainly of sandstones with interlayers of limestone and clay. The authors consider fifteen options of injecting ni-trogen into the reservoir, including options of treating the bottom-hole of low-production wells at the beginning of the process of further reservoir development and at the beginning of the injection of nitrogen into the reservoir. In all cases, the reservoir is first redeveloped in the depletion mode until the reservoir pressure decreases to 0,1 from the initial value. After that, nitrogen is injected into one of the producing wells which is transferred to the injection well. The injection of nitrogen into the reservoir continues until the nitrogen content in the last produc-ing well is less than 5 % vol. All options are characterized by high values of the gas recovery coefficient and close values of the dura-tion of the reservoir further development. The positions of the front of the displacement of natural gas by nitrogen at various time points are given. According to the research results, the gas recovery coefficient for tail gas for var-ious options varies from 14,12 to 34,58 %. With the introduction of the technology of injecting nitrogen into the reservoir, the overall gas recovery coefficient increases from 72,25 % (at present development system) to 80,28 % when the residual gas is displaced by nitrogen.

The Influence of the Characteristics of the Gas Reservoirs Perforation-Entering on the Well Production Capabilities

The main complications in the production of residual gas from depleted gas reservoirs are characterized. The deterioration of the formation pay zone in the depleted reservoirs occurs mainly due to the accumulation of liquid and particles and due to possible deformation of the rocks. One of the methods to reduce the effect of the for-mation bottom-hole zone contamination on the productive characteristics of wells is to create perforation tunnels in the bottomhole zone that can pass through the contaminated zone and improve the hydrodynamic connection of the gas-bearing reservoir with the well. The author studies the effect of the number and the size of perforation tun-nels (depending on the permeability of the reservoir at constant wellhead pressure) on the gas-well flow rate. The research results are presented in the form of graphical dependence of the ratio between the flow rate of the well with perforation channels and a hydrodynamically perfect well q/q0 on determining factors, as well as in the form of graphic relationships among individual determining factors. Using the research results, it is found that the ra-tional value of the diameter of the perforation channels should be at least 0,03 m, the channel lengths should not be shorter than 0,292-0,307 m and the number of channels per meter of the revealed reservoir thickness should be not less than 17-19 depending on the permeability of the formation. The number of perforation tunnels and their length de-crease with the growth of reservoir permeability according to the exponential law.

EXTRACTION OF THE RESIDUAL GAS DEPLETED GAS RESERVOIRS NITROGEN INJECTION

The relevance and feasibility of extracting residual gas from depleted gas deposits is shown. The possible directions of the extraction of residual gas from depleted gas deposits by its displacement from a porous medium of non-hydrocarbon gases are characterized. The use of nitrogen to displace natural gas from a porous medium has been substantiated. Using the GEM compositional modeling module, which is included in the licensed computer program CMG (Computer Modeling Group), studies were made of the effect of the pressure of the start of injection of nitrogen into the reservoir and the duration of its injection period on the gas recovery coefficient for residual gau. The study was conducted for deposits of square and round shape. The research results are presented in the form of graphical dependencies of the current reservoir pressure, nitrogen content in borehole products and gas recovery coefficient for residual gas from the pressure of the start of injection of nitrogen into the reservoir and the duration of the period of its injection. Using the results of the research, the optimal values ​​of the parameters of the process of injecting nitrogen into the exhausted gas deposits of square and round forms and the corresponding values ​​of the gas recovery coefficient were established. For the considered deposits of square and rounded forms, they are 0.29 Рin and 14.8 months, 0.31 Рin and 12.9 months, respectively. At the time of reaching the volumetric nitrogen content in the producing gas of 5 %, the gas recovery coefficient for residual gas for a square-shaped deposit is 83.91 %, for a round-shaped deposit – 77.49 %. The physical nature of the process of displacing residual gas with nitrogen from depleted gas deposits of square and round forms is characterized.