Sand Formation Research Articles

Linearized waveform inversion for vertical transversely isotropic elastic media: Methodology and multi-parameter crosstalk analysis

Seismic migration and inversion are closely related techniques to portray subsurface images and identify hydrocarbon reservoirs. Seismic migration aims at obtaining structural images of subsurface geologic discontinuities. More specifically, seismic migration estimates the reflectivity function (stacked average reflectivity or pre-stack angle-dependent reflectivity) from seismic reflection data. On the other hand, seismic inversion quantitatively estimates the intrinsic rock properties of subsurface formulations. Such seismic inversion methods are applicable to detect hydrocarbon reservoirs that may exhibit lateral variations in the inverted parameters. Although there exist many differences, pre-stack seismic migration is similar with the first iteration of the general linearized seismic inversion.Usually, seismic migration and inversion techniques assume an acoustic or isotropic elastic medium. Unconventional reservoirs such as shale and tight sand formation have notable anisotropic property. We present a linearized waveform inversion (LWI) scheme for weakly anisotropic elastic media with vertical transversely isotropic (VTI) symmetry. It is based on two-way anisotropic elastic wave equation and simultaneously inverts for the localized perturbations (ΔVp0/Vp0,ΔVs0/Vs0,Δϵ,Δδ) from the long-wavelength reference model. Our proposed VTI-elastic LWI is an iterative method that requires a forward and an adjoint operator acting on vectors in each iteration. We derive the forward Born approximation operator by perturbation theory and adjoint operator via adjoint-state method. The inversion has improved the quality of the images and reduces the multi-parameter crosstalk comparing with the adjoint-based images. We have observed that the multi-parameter crosstalk problem is more prominent in the inversion images for Thomsen anisotropy parameters. Especially, the Thomsen parameter δ is the most difficult to resolve. We also analyze the multi-parameter crosstalk using scattering radiation patterns.The linearized waveform inversion for VTI-elastic media presented in this article provides quantitative information of the rock properties that has the potential to help identify hydrocarbon reservoirs.

Late Pleistocene sea level change and tectonism control on the formation of the Old Red Sand along the southeastern coast of China

The Zhe-Min Uplift (ZMU) has undergone tectonic subsidence, which has been associated with a notable transgression in the northern marginal seas of China since the middle Pleistocene. However, its uplift history during the late Quaternary is still inadequate. The Old Red Sand (ORS) is a late Pleistocene deposit that is widely distributed along the southeastern coast of China. The ORS consists of partially-cemented fine- to medium-grained sand. In this paper, we focus on mud-rich ORS deposits of the Liushui area, Pingtan Island, Fujian Province, and report optically stimulated luminescence (OSL) ages, and new datasets of grain size, mineralogy (detrital zircon, clay and detrital minerals) and organic carbon and nitrogen isotope profiles to improve understanding of chronology, provenance, palaeoenvironmental evolution and tectonic infuence. Based on the OSL data, we hypothesize that the development of the ORS was associated with lower sea levels, with most deposition occurring within MIS4. Based on comparison of detrital zircon UPb ages, the coarse fraction of the Liushui ORS was mainly derived from the Minjiang River, with modest input from weathering of coastal granites. The East Asian Winter Monsoon contributed some materials from the East China Sea shelf during the last glacial period, as indicated by the fine-grained nature of the Liushui ORS, low K-feldspar/plagioclase ratios, high dolomite content and the frequency of Neoproterozoic and Palaeoproterozoic detrital zircons. The deposition of the ORS was influenced by both the East Asian Winter Monsoon and sea level changes. The clay minerals in the mud layers of the Liushui ORS were dominated by kaolinite and illite, with little chlorite and no smectite, indicating that they originated from the Minjiang River. The TOC/TN ratios of the mud layers, as well as their isotope characteristics, indicate the organic matter was derived from marine sources, presumably during the transgression event in MIS5. The average uplift rate of the ORS was about 0.03 mm/yr. The uplift of the ORS provided new insights into the geological records of the ZMU, which differed from the subsidence observed in the northern region of the Minjiang River during the late Pleistocene.

Investigation of the stress state of an elastic hollow ball during filtration of liquid through its wall

When determining the stress state of an elastic hollow ball when filtering liquid through its wall, it is necessary to solve the stress problem for the case of liquid filtration to the center of the ball with a decrease in pressure in its cavity. This case represents for us an element of the general problem of the stressed state of the annular filter behind the casing during well operation. First, the problem of liquid filtration is solved -pressure changes in the body under study are determined during liquid filtration. Then the equilibrium equation with respect to radial deformation is solved. A change in the sign of the filtration potential leads to a change in the tangential stresses on the well wall to a value equal to a tripled depression of reservoir pressure (with radial stresses equal to zero). This explains the negative effect of well shutdowns, and even more so the change in the direction of the filtration flow in the downhole part of the formation on the stability of the walls of wells, the operation of which is complicated by sand formation. The maximum difference of the main normal stresses is observed on the well wall, therefore, in order to prevent formation destruction near the bottom, a necessary condition is that the strength properties of rocks correspond to the stresses acting in this zone. When operating wells prone to plugging, it is necessary to limit the depression of reservoir pressure to the maximum permissible value when the material of the filter zone is in an elastic state throughout the volume.

Quaternary periglacial silicifications in the Paris Basin

In this paper, and in previous works, quartzites within the Sable de Fontainebleau are clearly shown to occur only near outcrops in Plio-Pleistocene plateau landscapes and are related to groundwater flows. These arrangements, together with dating of encased calcites, led us to consider that silicification occurred during Plio-Pleistocene glacial stages. The precipitation of silica was most likely triggered by cooling of groundwaters as they approached cold zones in the regolith close to points of discharge. We describe the arrangement and morphologies of quartzites in Tertiary sand formations in the Paris Basin to demonstrate how cold climates could have influenced hydrologic regimes and promoted silicification. The coeval precipitation of calcite and silica in gypseous formations at the edges of plateaux-bordering valleys, along with the dissolution of gypsum, also points to interactions between silica-laden groundwater and carbonate host rocks during cold periods. In parallel, the distribution and micromorphology of silicifications in associated Tertiary limestone formations suggests that they formed during cold climates in the Quaternary. These are key pointers to the role of groundwater in regolith environments in controlling silicification processes. We detail a link to palaeosurfaces of the distinctive meulières facies in the Paris Basin. Geotropic structures and micromorphological organisations are the basis of new ideas about their origin in a combination of vadose and phreatic environments and proximity to impervious cold horizons. The active zone in a permafrost landscape is a good hydrological example. All silicifications in Tertiary formations in the Paris Basin can be linked to the hydrology of Quaternary periglacial environments in a single model. This could apply more widely to similar silicifications elsewhere and be tested using new analytical techniques that date silicifications and unravel the isotopic relationships between silicification, groundwater composition and the prevailing climate.

The Use of Technology as the Indonesia's Strategy to Counter China's Gray Zone Operations in the North Natuna Sea

Ever since the end of World War II, the Republic of China (ROC), led by the Kuomintang Party and continued by the People’s Republic of China (PRC) led by the Communist Party, with its Eleven Dash Line (EDL), has claimed almost 90% of the South China Sea (SCS) waters, including the Spratly Islands, Paracel Islands, and all sea structures in that area. In 1953, the EDL was renamed to the Nine Dash Line (NDL) because China gave the area of the Tonkin Gulf to North Vietnam, led by Ho Chi Minh, which was still at war against the French and South Vietnam. China’s NDL claim has overlapped with Brunei’s claim, specifically Louisa Reef located on its continental shelf, Malaysia’s claim covering a portion of SCS in northern Kalimantan (Borneo), which includes at least 12 maritime structures in the Spratly Islands, among others, the coral reefs Swallow, Adraiser, and Marivelles. Additionally, the Philippines' claim includes the northernmost part of the Spratly Islands and Scarborough Shoal, known as Kalayaan in the Philippines. Vietnam's claim encompasses the Paracel and Spratly Islands, including 25 rock and sand formations and islands such as Spratly Island, Namyit Island, and Barque Canada Reef. The overlapping claims, which also occurred between Brunei and Vietnam, Malaysia and the Philippines, and Malaysia and Vietnam, have increased tension and incidents in the SCS, particularly between the Philippines, Malaysia, Vietnam against China due to China’s actions forcefully imposing its claim. This has made the situation more complex and fragile, leading the international community to term the overlapping claims as the South China Sea (SCS) Dispute. has no claim in the SCS, and no other country has a claim over Indonesia. However, in 2009, when China registered its new map of NDL claim with the United Nations (UN), it included part of Indonesia’s Exclusive Economic Zone (EEZ) in the North Natuna Sea (NNS). The UN rejected this claim since it was not based on international law, particularly the United Nations Convention on the Law of the Sea (UNCLOS 1982). Indonesia firmly denied that claim as it goes against Indonesia’s law and UNCLOS 1982. Due to increasing Chinese actions in imposing its claim on part of the IEEZ in the NNS, including Gray Zone Operations (GZO) maneuvers, Indonesia has risen to defend its sovereign rights in the NNS. According to UNCLOS 1982, in the IEEZ at the NNS, as a coastal state, Indonesia "has sovereign rights for the purpose of exploring and exploiting, conserving and managing the natural resources, whether living or non-living resources, of the waters superjacent to the sea-bed and off the sea bed and its subsoil, and with regard to other activities for the economic exploitation and exploration of the zone such as the production of energy from water, currents, and winds" (Article 56; 1 a). To overcome any disturbance and threat toward Indonesia’s sovereign rights in its EEZ in the NNS, Indonesia needs to convince China to nullify its IEEZ NNS’ claim. Indonesia needs to launch total diplomacy toward China, including cultural diplomacy, economic diplomacy, and defense diplomacy combined with and supported by defense capability. In this regard, Indonesia should increase its defense capability, particularly in the NNS, to guard the works, personnel, and equipment of the activities of natural resources exploration and exploitation. The enlargement of defense capability, including the quality and quantity of equipment and weaponry such as patrol boats, troopships, warships, hunter jets, fighter jets, radar systems, and Geographic Information Systems (GIS), should be done by optimizing the use of advanced technology. Determining the performance strategy, as well as the use of technology and interoperability systems in developing the defense equipment platform, information and communications technology such as Big Data and Data Links, can be a solution to increase and integrate the defense system, capability, and operational implementation. In this case, particularly by the Indonesia Navy and Air Force, by integrating various defense equipment owned and used. This study provides a comprehensive analysis of Indonesia’s strategy to counter China’s Gray Zone Operations in the North Natuna Sea.

Methodical approach to determining the maximum permissible velocity of the gas flow with mechanical impurities using numerical modeling of erosion processes of the main technological elements of wellhead equipment

Long-term operation of gas fields is accompanied by changes in the stress-strain state of the productive reservoir, including irreversible processes of its destruction. The destruction of a productive reservoir is one of the reasons for the removal of mechanical impurities at the wellhead, abrasive wear, metal degradation, the appearance of defects in pipelines, equipment and wellhead binding. In order to avoid serious consequences from the development of defects due to the removal of impurities, various examinations are carried out using non-destructive testing methods. The need to monitor the actual condition of pipelines and wellhead equipment of wells operating the Cenomanian and Valanginian formations is due to the fact that during operation significant damage and destruction of the main elements of technological equipment may occur due to the removal of mechanical impurities, water, as well as the formation of hydrates, sand jams, etc., this can lead to serious economic losses, as well as the negative impact on the environment as a result of leaky connections and assemblies. Thus, in order to ensure reliable operation of producing gas wells in conditions of destruction of the bottom-hole zone of the well, it is necessary to choose a reasonable technological mode of operation, in which the risk of formation of sand and liquid plugs is reduced, and the negative impact of the removal of impurities on the condition of the equipment is minimized. Keywords: gas well; numerical modeling; bottom-hole zone; technological mode.

PROVENANCE AND DISTRIBUTION OF MIDDLE BAONG SAND IN THE MALACCA STRAIT AND ITS SURROUNDING

The Middle Baong Sand Formation has long been ascribed to the Malay Peninsula. However, this contradicts the results of chronostratigraphic correlation and rare earth element (REE) analysis, which indicate another source from the south. This research was conducted in North Sumatra, especially in Pertamina's onshore and offshore work areas. The comparison area is located in Kutacane-Karo and the Malay Peninsula. The objective of the study is to understand the provenance of the Middle Baong Sand Formation in North Sumatra. Data from four wells and 32 outcrops are used to evaluate the provenance and distribution of Middle Baong Sand in the study area. Besides that, secondary data from three outcrops are also used to support the analysis. The methods used in this study are chronostratigraphic correlation and REE analysis. The results showed that the provenance of the Middle Baong Sand onshore is estimated to originate from southwest Sumatra, contrary to general assumptions. Validation was carried out by comparing Malay Peninsula data with Kutacane research data and wells using REE analysis. The analysis results showed that the Middle Baong Sand Formation in the onshore area has a different provenance from the Middle Baong Sand Formation in the offshore area, which contradicts other research conducted so far. Based on this study, it is concluded that the paleogeography of the North Sumatra basin undergoes deepening symmetrically in the central basin since 10.46 million years ago (Mya).

ESTIMATION OF AQUFER TRANSMISSIVITY FOR TYPICAL OIL PRODUCING COMMUNITIES OF WESTERN NIGER DELTA USING ELECTRICAL RESISTIVITY SURVEY

Geophysical electrical resistivity method (Vertical Electrical Sounding) using Schlumberger configuration was employed to investigate subsurface formations and aquifer transmisivity in Agbarotor, Agbarha-Otor and Edoiede Agbarha-Otor in Ughelli North Local Government Area in Delta State, Southern Nigeria with VES evenly carried out in the aforementioned study areas. ABEM Signal averaging system (SAS) 1000 Terrameter, was one of the major equipments used in obtaining the resistivity field data with a maximum current electrodes spreading of 500m done with the aid of a tape. The interpretation of the data gotten from the field was done using WINRESIST software coupled with the qualitative and quantitative curve matching to obtain modelize parameters and curves type for various VES points. The model parameters displayed up to six formations layers which include topsoil, laterite, clay and sand (fine, medium and coarse) formation. The resistivity of the confined aquifer ranges from 1037.6-4986.5Ωm with thickness varying interval of 16.3m and 42.9m. The investigation denote that VES 1 of Agbarotor, VES 6 for Agbarha-Otor and VES 7,9,10 of Edoiede Agbarha-Otor are the best locations for citing boreholes in the studied areas since they are characterize with higher resistivity (low corrosivity) and moderate or higher transmisivity. Thus aquifer transmisivity in the cited areas are of good quality and the produce can sustain the people of the areas and neighboring environs for long period of time. I recommend that the samples of VES water locations should be tested from time to time to ascertain its Level of contaminations for future remedial measure and a water system for the general public should be drilled in the aforementioned VES points.

Assessment of Potential Potable Water Reserves in Islamabad, Pakistan Using Vertical Electrical Sounding Technique

This study aimed to investigate the potential reserves of potable water in Islamabad, Pakistan, considering the alarming depletion of water resources. A detailed vertical electrical sounding (VES) survey was conducted in two main localities: Bara Kahu (Area 1) and Aabpara to G-13 (Area 2), based on accessibility, time, and budget constraints. A total of 23 VES measurements were performed, with 13 in Area 1 and 10 in Area 2, reaching a maximum depth of 500 m. Geologs and pseudosections were generated to assess lithological variations, aquifer conditions, and resistivity trends with depth. Statistical distribution of resistivity (SDR), hydraulic parameters, true resistivity, macroanisotropy, aquifer depth and thickness, and linear regression (R2) curves were calculated for both areas, providing insights into the aquifer conditions. The results revealed that the study areas predominantly consisted of sandy lithology as the aquifer horizon, encompassing sandstone, sandy clay, and clayey sand formations. Area 2 exhibited a higher presence of clayey horizons, and aquifers were generally deeper compared to Area 1. The aquifer thickness ranged from 10 m to 200 m, with shallow depths ranging from 10 m to 60 m and deeper aquifers exceeding 200 m. Aquifers in Area 1 were mostly semi-confined, while those in Area 2 were predominantly unconfined and susceptible to recharge and potential contamination. The northwest–southeast side of Area 1 exhibited the highest probability for ground resource estimation, while in Area 2, the northeast–southwest side displayed a dominant probability. The study identified a probable shear zone in Area 2, indicating lithological differences between the northeast and southwest sides with a reverse sequence. Based on the findings, it is recommended that the shallow aquifers in Area 1 be considered the best potential reservoir for water supply. In contrast, deeper drilling is advised in Area 2 to ensure a long-lasting, high-quality water supply. These results provide valuable information for water resource management and facilitate sustainable water supply planning and decision making in Islamabad, Pakistan.

IMPROVED SEISMIC IMAGING THROUGH PETROPHYSICAL APPROACH USING THOMSEN'S PARAMETER ESTIMATION IN ANISOTROPIC PRESTACK DEPTH MIGRATION (PSDM)

Research has been carried out using the Prestack Depth Migration (PSDM) anisotropy method for 2D reflection seismic data. This research aims to estimate anisotropic parameter values with a petrophysical approach to the Prestack Depth Migration method to obtain better imaging results. The type of anisotropic medium used is Vertical Transverse Isotropy (VTI) because that can explain the effect of anisotropy in a simple form on the sediment layer. In theory, 2 parameters are needed to describe this parameter, namely ε and δ. δ is an anisotropic parameter that describes the velocity variation towards a nearly vertical direction and is the control depth of seismic. In contrast, ε describes the velocity variation towards the near horizontal direction. The stages of data processing are divided into two; the first is PSDM isotropy, which flattens gather at near offset (angle mute <30 degrees), and PSDM anisotropy to flatten-gather at far offset (mute angle> 30 degrees). The results of this study showed that the relation of ε and δ in shale formations was (δ = 0.4958ε - 0.0152) and sand formation (δ = 0.9082ε - 0.0203) and the range of anisotropic parameters δ and ε were -0.02 up to 0.13 and 0 up to 0.3. From all ranges of anisotropic parameter values, this study belongs to the "weak anisotropy" category Thomsen (0 to 0.5). The value of anisotropy parameters obtained can give the results of seismic images more accurately and clearly than PSDM isotropy. It can correct errors in the depth of seismic up to 51 m.

Optimization of the Grout Mix Ratio and Simulation Test of Shield Tail Grouting Similarities in a Water-Rich Fine Sand Layer

When shield tunneling is performed in water-rich silt and fine sand strata, the grout becomes runny when diluted by groundwater. After dilution, the filling effect of the grout is not significant, and the level of surface settlement is very high. In this study, based on bidding section 04 of Tianjin Metro Line 11, traditional grouting materials were selected to conduct response surface method (RSM) tests. The purposes of the RSM analysis were to analyze the interactions between materials and their influences on grout performance and to optimize the grout mix ratio. Various admixtures were compared to assess the effects of different admixtures and compositions on the dispersion resistance and flow performance of the grout. Finally, a shield synchronous grouting test system was developed, and a similar indoor grouting simulation test was performed to analyze the influences of the different admixtures on the filling effects and to determine a reasonable grout mix ratio. The following three results were obtained. (1) The RSM was suitable for grout performance prediction and grout mix ratio optimization, and hydroxyethyl cellulose could improve the grout performance and increase the bond performance between the cementing material and aggregate. (2) Admixture incorporation enhancement could improve the grout utilization rate and increase the diffusion distance at the top of the tunnel, which would be conducive to filling the gap at the tail end of the shield. (3) The optimal preparation scheme of grout in water-rich fine sand formations included a water–binder ratio of 0.72, cement–sand ratio of 0.80, fly ash content of 5%, bentonite content of 14.94%, and admixture content of 0.8%–0.9%

Elastic properties of unconsolidated sandstones of interest for carbon storage

AbstractUnconsolidated sandstones are attractive targets for underground storage of carbon due to their high porosity and permeability. Monitoring of injection and movement of CO2 in such formations using elastic waves requires an understanding of the acoustic properties of the sandstone. Current approaches often use the so‐called soft‐sand model in which a Hertz–Mindlin model of the acoustic properties at high porosity is mixed with the acoustic properties of the mineral phase to predict the acoustic properties over the entire porosity range. Using well‐log data from two unconsolidated sand formations of interest for CO2 storage, we discuss the limitations of this model and provide an alternative approach in which the mechanical properties of grain contacts are obtained by inversion, and the properties of infill material lying within the pore space are estimated. The formations considered are the Paluxy Formation in Kemper County, Mississippi, and the Frio Formation near Houston, Texas. The ratio of the normal to shear compliance of the grain contacts is found to be significantly less than unity for both formations. This implies that the grain contacts are more compliant in shear than in compression. However, the grain contact compliance is higher and the ratio of the normal to shear compliance is lower for the Frio example than for the Paluxy case, and this may lead to sliding at grain contacts with low shear compliance and transport of grains during fluid flow, particularly if CO2 acts to weaken any cement that may be present at the grain contacts. Such transport was suggested by Al Hosni et al. in explaining why the magnitude of the time‐lapse effect due to the injection of CO2 at the Frio CO2 injection site is greater than predicted using conventional rock physics models. A simple model of the mechanical properties of infill material lying within the pore space suggests that the bulk and shear moduli of infill material in the Paluxy case are significantly higher than the Frio case, consistent with the lower grain contact compliance in the Paluxy case.

A Study on a New Type of High-Performance Resin-Coated Sand for Petroleum Fracturing Proppants

This study investigates a new type of high-performance coated sand as a petroleum fracturing proppant material. Modified quartz sand was coated with a layer of low-density resin to reduce the overall density of the proppant, thereby improving the suspension of the proppant in the fracturing fluid. Resins play an important role in the preparation of coated sand fracturing proppants. The mechanism of sand formation was studied by examining the phase composition and microstructure of the coated sand proppant. The results demonstrate that when the polyimide resin content is 6% and the curing temperature is 180 °C, the proppant exhibited the best performance with an apparent density of 1.592 g/cm3 and a breakage ratio of only 3.22% under 55.2 MPa. Compared with the widely used epoxy resin-coated support agent and phenolic resin-coated support agent in the early stage, their crushing rate decreased by 5% and their acid solubility decreased by 2%. Hence, this study is worthy of attention.

Revised models for evaluating hydrocarbon saturation of tight sandstone formations based on dielectric dispersion logs

AbstractAccurate estimation of hydrocarbon saturation is significant for log interpreters to evaluate tight sandstone formations. It is difficult to use conventional wireline logs to calculate hydrocarbon saturation in complex reservoirs. Dielectric dispersion logs are processed using dielectric models to obtain accurate saturation assessment, especially in high salinity shaly sand formations. However, the dielectric models consist of complex refractive index method model and shaly sand model ignore the impact of clay effects on complex refractive index method model, and the dielectric dispersion logs generated by them appear several unphysical phenomena in the clay‐bearing formations, such as the permittivity data at the highest frequency are greater than those at the second highest frequency and the conductivity data at the highest frequency are lower than those at the second highest frequency. This paper modifies the dielectric models by introducing a combined conductive phase in complex refractive index method model to correct the unphysical behaviours. Revised models are combined with four permittivity and four conductivity logs acquired by dielectric scanner at 24, 102, 360 and 960 MHz to inverse the water saturation, water salinity, textural index for water‐bearing pore and fraction of clay‐related phase. The complex refractive index method model interprets the logs measured at 960 MHz and shaly‐sand model interprets other dielectric dispersion logs. The particle swarm optimization algorithm is used to search inversion parameters. The results of forward simulation show that the revised models can correct unphysical behaviours of dielectric dispersion logs generated by the original models. Moreover, we apply original models and revised models to laboratory core data. The results of experiments show that the mean relative error values of the original models are 19.38% and 23.60% and of the revised models are 5.54% and 6.28% in two cases. It shows that the revised models are more accurate than the original models to interpret dielectric dispersion logs of tight sandstone reservoirs.

A gel system with long‐term high‐temperature stability for deep profile modification of high‐temperature oil and gas reservoirs

AbstractProfile modification is the key for efficient development of oil and gas reservoirs, especially high‐temperature reservoirs, which requires the system to have good high‐temperature resistance. According to the characteristics of high‐temperature reservoir, a high temperature gel composed of terpolymer, modified phenolic resin, aromatic amine curing agent and thiourea was developed. The effects of different components on the properties of the gel system were clarified. Then, the long‐term thermal stability under high‐temperature conditions was studied. In addition, the plugging performance of gel system under different permeability and injection volume was studied. Finally, the gelation properties and plugging properties of gel system with the flow distance were studied by simulating the flow of porous media. The results show that the gel system has high strength and suitable gelation time, and it can be adjusted in real time according to different oilfield requirements. In the range of 75–150°C, the gel system had excellent long‐term stability. When the temperature was 75°C, no free water after 120 days, and the viscosity only decreased from 13,131 to 11,254 mPa·s. Even at 150°C, the viscosity was as high as 8350 mPa·s after 120 days, and the free water was only 5.5%. The gel system had good adhesion ability on the porous media surface and strong anti‐flooding properties. When the injection volume was 0.1 pore volume (PV in short), the plugging rate to the sand packed tube was 72.7%. When the injection volume was 0.5 PV, the plugging rate was as high as 97.6%. The plugging rate of the gel system for the sand packed tube with permeability of 500 mD was 98.7% when the injection volume was 0.5 PV. When the permeability increased to 3000 mD, the plugging rate still reached 92.3%. The gel system also had an excellent deep profile control ability, and the viscosity retention of at 60 cm was as high as 96%. When the flow distance was 2 m, the viscosity retention also reached 75%. The rheological properties also shown that the gel system had excellent shearing resistance and adsorption resistance. Finally, combined with the state of the gel system on the surface of the porous media, there was no cementation between the formation sand before the injection, and the sand particles did not stick to each other. After the gel was injected, the adhesion of gel system on the porous media surface was very strong. The 3D network structure was also very dense, the sand particles could have good cementation effect under the adhesion of gel system.

TotalEnergies Drills Lebanon’s Qana Prospect Amid New Global Interest in EastMed Gas

_ As of September, TotalEnergies together with partners Eni and QatarEnergy will have spud exploration well 31/1 on Block 9 of Lebanon’s Qana prospect. It is the consortium’s second attempt in 6 years to strike gas in the EastMed where upstream riches at the crossroads of markets east and west struggle against the fiercest of global geopolitical headwinds. Lebanese media hailed the 16 August arrival of the Transocean Barents semisubmersible drilling platform at Block 9 with guarded optimism, reporting on the Barents journey from the North Sea like a sports play-by-play, detailing the landing of the first crew transport helicopter and the offloading of pipe and other equipment delivered by ship to the Port of Beirut. The Lebanese Petroleum Administration busily dotted the i’s and crossed the t’s on the drilling license application that TotalEnergies EP Lebanon had submitted in June while MP Ibrahim Kanaan, head of the parliament’s finance and budget committee, announced creation of the Lebanese Sovereign Fund for Oil and Gas to protect future revenues from political interference. “The rig will start working in Lebanon in September ... before the end of the year we will know if there is a discovery,” Lebanon’s caretaker Energy Minister Walid Fayyad told Reuters at an event earlier this summer in Abu Dhabi. Built to operate in harsh environments the Barents will drill in deep water, its crew hoping to hit the sweet spot that is the Tamar Sands Formation from which Israel, Cyprus, and Egypt are already producing gas for domestic needs and for export. Assuming commercial gas reserves are confirmed in Qana, Lebanon will join the club of EastMed gas producers—a development that would ease Beirut’s seemingly endless energy crisis, give the financially bankrupt country a share of revenues for gas exported to Europe and Asia, and attract further global investment. The World Bank has described Lebanon’s economic collapse as possibly one of the top three most severe worldwide since the 1850s. But while all seems like business as usual, this is the EastMed where political and military conflicts that dog oil and gas projects throughout the world can escalate quickly, driven by political fragmentation and violence within and across borders of countries with the most to gain from big international projects. What might be called a harsh environment in the UK sector of the North Sea where the Barents worked most recently differs greatly from what can be called harsh in the EastMed where technology can’t solve all of a hydrocarbon project’s problems. Drawing Lines in the Sand Beirut awarded exploration licenses in 2017 to drill on its offshore Blocks 4 and 9 to the Total-lead consortium with Eni and, at the time, Russia’s independent gas producer and LNG exporter Novatek. This past January, QatarEnergy farmed in for a 30% stake after Novatek exited. TotalEnergies and Eni each now hold 35%. In the 6 years following the license award, the consortium drilled only one well on the Lebanese shelf—a dry hole on Block 4 in 2020. Though data suggested that the Qana prospect in Block 9 might be different, TotalEnergies delayed further appraisal drilling pending settlement of the maritime boundary between Israel and Lebanon.

A new method for calculating the minimum sand-carrying velocity in geothermal well production

Formation sand production is an important engineering and technical problem that restricts the safe and efficient development of geothermal wells. Accurate prediction of the minimum sand carrying velocity of sand production is the key to effectively controlling the formation sand production of geothermal wells. Compared with conventional vertical well sand production, geothermal wellbore sand carrying has the characteristics of high concentration, high fluid temperature, and easy silting, which makes it more difficult to calculate the minimum sand carrying velocity. In order to derive the formula of sand carrying law suitable for complex geothermal conditions, this paper considers the temperature and concentration conditions, based on the basic sedimentation principle and indoor sand carrying experiment, abandons the single correction coefficient correction of the conventional calculation formula, integrates the influence of temperature and high sand content on debris migration and deposition, and adopts the double correction coefficient of temperature-viscosity and sand content-mixed density, the actual minimum sand carrying velocity calculation formula of geothermal well under different sand content and temperature is obtained, and a new theoretical calculation method of minimum sand carrying velocity of the geothermal wellbore is formed. With the help of indoor experiments, a reasonable experimental group was designed to carry sand law experimental research. The experimental results show that the calculated value is in good agreement with the measured data, and can be used to calculate the minimum sand-carrying velocity of unconsolidated sandstone in the geothermal wellbore, which provides a basis for sand-carrying failure and sand sinking prevention in geothermal wellbore site.

Estimation of natural methane emissions from the largest oil sand deposits on earth.

Worldwide methane emission by various industrial sources is one of the important human concerns due to its serious climate and air-quality implications. This study investigates less-considered diffusive natural methane emissions from the world's largest oil sand deposits. An analytical model, considering the first-order methane degradation, in combination with Monte Carlo simulations, is used to quantitatively characterize diffusive methane emissions from Alberta's oil sands formations. The results show that the average diffusive methane emissions from Alberta's oil sands formations is 1.56 × 10-4 kg/m2/year at the 90th percentile of cumulative probability. The results also indicate an annual diffusive methane emissions rate of 0.857 ± 0.013 Million tons of CO2e/year (MtCO2e/year) from Alberta's oil sands formations. This finding suggests that natural diffusive leakages from the oil sands contribute an additional 1.659 ± 0.025 and 5.194 ± 0.079% to recent Canada's 2019 and Alberta's 2020 methane emission estimates from the upstream oil and gas sector, respectively. The developed model combined with Monte Carlo simulations can be used as a tool for assessing methane emissions and current inventories.

Selective oil saturation of Verkhnechimidikeenskoe oil manifestation

The article considers the problem of possible oil-bearing of the section’s upper part in the area of permafrost’s distribution on the example of the north-east of the Siberian platform. The actual data testifying to the existence of permeable intervals in the permafrost rocks (PFR) are presented. The main attention is paid to the unusual «hanging» distribution of oil inside the sand formation. This low-thickness lower Jurassic formation contains a concentration of oil of a lensoid shape. At the same time unaltered areas of the sand formation (without saturation) surrounding top and bottom saturated part do not differ in lithological characteristics. The assumption about the relevance of the Verkhnechimidikeenskoe Oil Manifestation to the relic inter-permafrost aquifer is made. As a modern analogue, the sufficiently detailed distribution zone of inter-permafrost aquifers on the northern slope of the Aldanskaya anteclise with similar lithological-stratigraphic performance is briefly described.

Assessing Contaminant Mass Discharge Uncertainty With Application of Hydraulic Conductivities Derived From Geoelectrical Cross‐Borehole Induced Polarization and Other Methods

AbstractA new methodology was developed to support contaminant mass discharge (CMD)‐based risk assessment of groundwater contamination downgradient of point source zones. Geoelectrical cross‐borehole induced polarization (IP) data were collected at a site undergoing in situ remediation of chlorinated solvents for determining 2D hydraulic conductivity (K) distributions with an inversion model resolution of 0.15 m (vertically) x 0.50 m (horizontally) in three control planes from 10 to 20 m depth. Additionally, 18 slug tests and 31 grain size distribution analyses (GSA) from the control planes, were used for K‐estimation. The geometric means and variance of the IP, slug test, and GSA derived K‐estimates were consistent with previously studied sandy aquifers. Furthermore, the vertical variation in K between two geological settings, a sandy till and a meltwater sand formation, was clearly identified by the IP K‐estimates. The vertical variation was backed up by hydraulic profiling tool (HPT) measurements. Random realizations of CMD were simulated based on the cross‐borehole IP derived K‐values. For comparison, the CMD was also estimated with a geostatistical conditional simulation approach, using the data from slug tests and GSAs. The high IP resolution captured the small scale variations in K across the transects and led to CMD predictions with a narrow uncertainty interval, whereas slug test and GSA either under‐ or overestimated the magnitude of the areas with the highest CMD. Applying the geophysical cross‐borehole method for estimating K‐distributions in addition to traditional methods would improve CMD‐based risk assessment and evaluation of remediation performance at contaminated sites.