Reservoir Drainage Research Articles

Magma fizz: Tremor during the Kīlauea summit reservoir decompression

Typical eruptions at Kīlauea volcano involve the evacuation of magma from the summit and/or south caldera reservoirs towards the East or Southwest rift zones. The reservoir drainage provokes the summit deflation, and on extreme occasions, such as in 2018, the summit caldera collapse. Systematically, seismic tremor, often with a particular multichromatic spectral signature characterized by frequency gliding, accompanies summit deflation episodes. In 2018, this type of continuous tremor accompanied the steady subsidence stage, whereas discrete earthquakes dominated the collapse stage. In this work, we aim to understand the source mechanism of the syn-deflation tremor of 2018. To locate the seismic source, we develop a novel machine-learning-based algorithm as an alternative to the amplitude source location technique. We use a large high-resolution catalog to resolve a composite amplitude decay function. Under these conditions, our method outperforms the traditional technique. We locate the tremor source 1 km below the eastern perimeter of the Halema‘uma‘u crater, which coincides with the position of the summit magma reservoir, as determined in many other studies. Furthermore, we model the seismic source as pressure oscillations driven by gas porous flow at the roof of the reservoir. In this model, gas accumulates temporarily in many gas pockets between the magma and the roof. Our modeling shows that the gas flux is responsible for the tremor amplitude modulations, whereas the gas pocket thickness controls the frequency variations. Beyond a critical point of depressurization, the magma cannot contribute further to the tremor oscillations via decompression-driven degassing, nor support the roof above it, resulting in rock failure. This work advances our understanding of magma-degassing dynamics and tremor generation at Kilauea volcano, and provides novel seismological techniques for volcano seismology monitoring and research.

Environmental consequences of the creation and discharge of reservoirs in the steppe zone

The article examines the environmental consequences of the construction and operation of reservoirs – the responses of aquatic and terrestrial ecosystems and their components to changes in the water regime. Such reactions depend on the surrounding landscape and are zonally specific. They are especially pronounced in the steppe zone. The authors systematized the consequences, natural and anthropogenic factors determining their evolution, measures to minimize negative environmental consequences that can be traced from the upper reaches of the reservoir to the reservoir – receiver of the river flow, where it is built. In particular, the decrease in bioproductivity and biodiversity caused the problem of reservoir drainage. As a result of lengthy discussions, an opinion has been formed that the descent of small reservoirs, which have lost their importance, as well as orphan ones, is currently environmentally justified. At the same time, it is necessary to carry out special hydro-reclamation and phytomeliorative measures aimed at stabilizing the hydrological and ecological situation.

Extensive glacitectonism and rapid deglacial fluid expulsion in the northeastern Barents Sea

High-latitude regions store large amounts of carbon trapped by ice sheets, permafrost and gas hydrates, yet joint evolution of these climate components is poorly understood. Covered by a cold-based ice-sheet during the last glaciation, the seafloor of the northeastern Barents Sea reveals one of the largest known glacitectonic provinces in the Arctic. Up to 200-m high glacitectonic landforms are cratered and overlie faults associated with ‘bright spots’ indicative of subsurface gas accumulations. However, sediment samples show low pore gas concentrations and no present-day gas seepage. We combine new observations and ice-sheet - hydrate modelling to propose that during the Late Weichselian, glacitectonism was caused by patchy substrate stiffening due to gradual growth of subglacial gas hydrates and permafrost. Ice decay led to rapid destabilisation and full drainage of shallow hydrate reservoirs and permafrost thaw, causing craterisation which was likely accompanied by large fluxes of carbon released into the water column. This study shows that these processes were more widespread across glaciated margins, also highlighting sensitivity and potential for abrupt changes of high-latitude carbon pools in response to complex interactions between the cryosphere, ocean, and solid earth.

Effects of microstructure on hydraulic fracturing and gas–water production in coal reservoirs: A case study of the Dahebian coalbed methane block in Western Guizhou, China

AbstractThe development of coalbed methane (CBM) in China is susceptible to the influence of microstructure. Therefore, it is crucial to understand the extension laws of hydraulic fractures and engineering responses in coal reservoirs affected by microstructure development. Utilizing the Dahebian block in western Guizhou as the study area, this investigation examines the coal reservoir characteristics, fracturing, and drainage engineering analysis of the well DC1 group in the region. The aim is to discuss the spatial distribution characteristics of hydraulic fractures, geological controlling factors influenced by microstructure, and their corresponding engineering responses. The results indicate that, for coal reservoirs unaffected by microstructure, the extension laws of the fracture network in both longitudinal and planar directions are influenced by burial depth and the regional stress field. In the microstructural belt, tectonic stress dominates, causing changes in the ground stress field. Consequently, the hydraulic fracture network deviates from the direction of the maximum principal stress during the extension process. When a secondary fracture is nearby, the hydraulic fracture network extends towards the shortest path radial secondary fracture direction, leading to a rapid increase in fracture width per unit length until it intersects with the secondary fracture. Additionally, the presence of secondary joints near the microfault structure decreases fracturing pressure and results in a dense distribution of the fracture network. This promotes the formation of a complex fracture network, favorable for fracturing. The extension of the fracture network in complex structural development areas is influenced by the microfault structure between wells, which is reflected in the fracturing construction pressure and fluid output. This accounts for the significant variations in the early drainage performance of CBM wells.

On the ice induced damage of reservoir drainage tower: A thermal stress-involved contact simulation

Ice thermal stress is an important factor causing damage to reservoir structures (e.g., drainage towers) in cold regions. It is very important to reveal the damage mechanism of ice thermal stress on reservoir structures to prevent such damage. The key to understanding this mechanism is to figure out the contact force between ice and structure. However, existing models do not investigate how changes in temperature and friction coefficient affect the contact force. In order to solve these problems, this paper proposes a thermal stress-involved contact model to simulate the ice-induced structural damage process of reservoirs by integrating the effects of ice temperature, composition and friction coefficient. The friction coefficient is innovatively written as a function of temperature and contact force. The simulation results are consistent with the real ice-induced structural failure of the LJZ reservoir. The agreements between the simulations and engineering observations show that the model can precisely mimic the structural damage process caused by the thermal stress of ice. The temperature-dependent friction coefficient, which changes with temperature, significantly affects the thermal stress and ice displacement results. Therefore, it is imperative to account for the friction coefficient's temperature-dependent variation. In addition, the effects of different temperature rise rates and different boundary conditions on thermal stress and displacement in ice are analyzed. Measures are proposed to prevent damage to the structure due to changes in the boundary conditions.

Multiple isotopes decipher the nitrogen cycle in the cascade reservoirs and downstream in the middle and lower Yellow River: Insight for reservoir drainage period

Intensive anthropogenic activities, such as excessive nitrogen input and dam construction, have altered the nitrogen cycle in the global river system. However, the focus on the source, transformation and fate of nitrogen in the Yellow River is still scarce. In this study, the multiple isotopes (δ15N-NO3−, δ18O-NO3−, δ15N-NH4+ and δ15N-PN) were deciphered to explore the nitrogen cycling processes and the driving factors in the thermally stratified cascade reservoirs (Sanmenxia Reservoir: SMXR and Xiaolangdi Reservoir: XLDR) and Lower Yellow River (LYR) during the drainage period of the XLDR. In the SMXR, algal bloom triggered the assimilation process in the upper layer before the SMX Dam, followed by remineralization and subsequent nitrification processes in the lower water layers. The nitrification reaction in the XLDR progressively increased along both longitudinal and vertical directions to the lower layer of the XLD Dam, which was linked to the variation in the water residence time of riverine, transition and lentic zones. The robust nitrification rates in the lower layer of the lentic zone coincided with the substantial depletion of nitrate isotopic composition and enrichment of both δ15N-PN and δ15N-NH4+, indicating the longer water residence time not only promoted the growth of the nitrifying population but also facilitated the remineralization to enhance NH4+ availability. In the LYR, the slight nitrate assimilation, as indicated by nitrate isotopic composition and fractionation models, was the predominant nitrogen transformation process. The Bayesian isotope mixing model results showed that manure and sewage was the dominant nitrate source (50 %) in the middle and lower Yellow River. Notably, the in-reservoir nitrification was a significant nitrate source (27 %) in the XLDR and LYR. Our study deepens the understanding of anthropogenic activities impacting the nitrogen cycle in the river-reservoir system, providing valuable insight into water quality management and nitrogen cycle mechanisms in the Yellow River.

Influence of land use on spatial distribution of mobile phosphorus forms in the sediment of a tropical semi-arid reservoir

Changes in land use and land cover influence the transport of nutrients, mainly phosphorus (P), to aquatic ecosystems. P can be available in the water column to primary producers' assimilation or be stored in different forms in limnic sediment. Therefore, this study aims to analyze the impact of land use and land cover on the spatial distribution of phosphorus forms in the sediment of a tropical semi-arid reservoir. We hypothesize that agriculture, exposed soil and the presence of floodable vegetation increase the amount of mobile phosphorus in the sediment and the sediment closer to the dam show a greater amount of mobile phosphorus due to the confluence of the flows. The classification of land use and land cover was carried out through supervised analysis at the level of the reservoir's drainage basin and area of influence. Sediment samples from the reservoir were collected at four different sampling points within the influence of two sub-basins. P forms were obtained through chemical fractionation of these sediment samples along the reservoir. Sparse Caatinga was the predominant land cover in the drainage basin and in the influence area, accounting for >50 % of these areas. This land cover represents a risk for nutrient transport to aquatic environments. The sediment samples from Boqueirão reservoir exhibited a high amount of phosphorus, mainly in the mobile forms. These forms were heterogeneously distributed throughout the reservoir. Agriculture activities, exposed soil, and floodable vegetation, influence the distribution and increase of mobile forms of phosphorus in the reservoir sediment. This suggests the need for specific strategies for manage these activities properly. Additionally, the sediment closest to the dam showed a lower amount of mobile phosphorus compared to samples further upstream.

Combination of Conventional EVD and Ommaya Drainage for Intraventricular Hemorrhage (IVH).

The effect of Ommaya reservoirs on the clinical outcomes of patients with intraventricular hemorrhage (IVH) remains unclear. We aimed to determine the effect of combining the Ommaya reservoir and external ventricular drainage (EVD) therapy on IVH and explore better clinical indicators for Ommaya implantation. A retrospective analysis was conducted on patients diagnosed with IVH who received EVD-Ommaya drainage between January 2013 and March 2021. The patient population was divided into two groups: the Ommaya-used group, comprising patients in whom the Ommaya drainage system was activated post-surgery, and the Ommaya-unused group, comprising patients in whom the system was not activated. The study analyzed clinical, imaging, and outcome data of the patient population. A total of 123 patients with IVH were included: 75 patients in the Ommaya-used group and 48 patients in the Ommaya-unused group. The patients in the Ommaya-used group showed a lower 3-month GOS than those in the Ommaya-unused group (p<0.0001). The modified Graeb scale (mGS) in the Ommaya-unused group was significantly lower than that in the Ommaya-used group before the operation (p<0.01) but not after surgery (p>0.05). The GCS in the Ommaya-unused group was significantly lower than that in the other group, and there was a close correlation between the GCS and 3-month GOS (p<0.0001). The GCS score showed significance in predicting the use of Ommaya (p<0.001). The study demonstrated that combining EVD and Ommaya drainage was a safe and feasible treatment for IVH. Additionally, preoperative GCS was found to predict the use of Ommaya drainage in subsequent treatment, providing valuable information for pre-surgery decision-making.

Numerical modeling for mining dam cover infiltration design with geosynthetics: A trade off study

In the mining dam closure project, depending on the classification of the tailings, cover systems are used to reduce precipitation infiltration over time, avoiding future environmental impacts associated with metal leaching. Furthermore, reduced infiltration promotes reservoir drainage and therefore improved geotechnical stability. The covering system can be built from different materials, natural or synthetic, or even using waste itself. The main objective of this study is to present the results as a trade-off study of a one-dimensional modeling performed considering 3 configurations of geosynthetic covers, using the SOFTWARE SEEP/W emphasizing the importance and impact of the presence of geosynthetics. Since numerical models constitute an essential tool in the development of engineering projects, computational numerical modeling was carried out using Brazilian climatic parameters from the National Institute of Meteorology in conventional and automatic stations, and historical geotechnical parameters for a structure located in the state of Minas Gerais. Gerais (Brazil). For the comparison of the cover configurations, the thickness and type of the geosynthetic were varied. The results emphasize the importance of studying numerical modeling in the pre-closure design phase, to define a viable, economical and sustainable coverage, and contribute to the use of geosynthetics in this type of application.

Intraoperative Extracorporeal Support during Lung Transplantation: Not Just for the High-Risk Patient.

The use of intraoperative mechanical support during lung transplantation has traditionally been a controversial topic. Trends for intraoperative mechanical support strategies swing like a pendulum. Historically, cardiopulmonary bypass (CPB) was the modality of choice during transplantation. It provides full hemodynamic support including oxygenation and decarboxylation. Surgical exposure is improved by permitting the drainage of the heart and provides more permissive retraction. CPBs contain drainage reservoirs with hand-held pump suction catheters promoting blood conservation through collection and re-circulation. But CPB has its disadvantages. It is known to cause systemic inflammation and coagulopathy. CPB requires high doses of heparinization, which increases bleeding risks. As transplantation progressed, off-pump transplantation began to trend as a preferable option. ECMO, however, has many of the benefits of CPB with less of the risk. Outcomes were improved with ECMO compared to CPB. CPB has a higher blood transfusion requirement, a higher need for post-operative ECMO support, a higher re-intubation rate, high rates of kidney injury and need for hemodialysis, longer ICU stays, higher incidences of PGD grade 3, as well as overall in-hospital mortality when compared with ECMO use. The focus now shifts to using intraoperative mechanical support to protect the graft, helping to reduce ischemia-reperfusion injury and allowing for lung protective ventilator settings. Studies show that the routine use of ECMO during transplantation decreases the rate of primary graft dysfunction and many adverse outcomes including ventilator time, need for tracheostomy, renal failure, post-operative ECMO requirements, and others. As intraoperative planned ECMO is considered a safe and effective approach, with improved survival and better overall outcomes compared to both unplanned ECMO implementation and off-pump transplantation, its routine use should be taken into consideration as standard protocol.

Assessing Dengue Hemorrhagic Fever Risk: Insights from Behavioral Aspects and Home Environmental Conditions

As the provincial capital, Jambi City has witnessed rapid development, evident in the construction of 5,000 housing units between 2019 and 2021 amid the COVID-19 pandemic. However, if left unoccupied, these settlements could potentially become breeding grounds for mosquito larvae, particularly Aedes aegypti, contributing to the escalating dengue cases in the city. This study aims to analyze the risk factors for dengue hemorrhagic fever based on behavioral aspects and environmental conditions. Conducted in the Pinang Merah Alam Barajo Urban Village of Jambi City, this observational analytic study involved 108 randomly selected respondents. The research data underwent analysis using the chi-square test, with statistical significance set at ≤ 0.05. The findings revealed that most community behaviors fell into the 'good' category, including habits like hanging clothes, collecting rainwater around the house, using abate powder in water reservoirs, weekly drainage of water reservoirs, proper disposal of used items, monitoring of larvae through cards, and keeping larvae-eating fish. The incidence of dengue hemorrhagic fever was significantly associated with hanging clothes indoors (p=0.000), collecting rainwater around the house (p=0.004), and draining water reservoirs once a week (p=0.004). However, no significant associations were found with the use of abate powder (p=0.380), disposing of used goods (p=0.087), monitoring larvae with cards (p=0.134), and keeping fish (p=0.122). In conclusion, the study highlights a strong correlation between dengue hemorrhagic fever and certain behaviors, notably hanging clothes indoors, collecting rainwater around the house, and draining water reservoirs on a weekly basis. Keywords: Dengue, Aedes Aegypti, Behavior, Vector

Key technologies and orientation of EGR for the Sulige tight sandstone gas field in the Ordos Basin

The Sulige Gas Field in the Ordos Basin is the largest tight gas field in China, with proved reserves exceeding 2 × 1012 m3. As the main contributor to gas production in PetroChina Changqing Oilfield Company, The Sulige Gas Field is in the stage of stable production. Maximizing the stable production period is a focus and challenge for the gas field now. To address a series of problems influencing the efficient development of Sulige gas field, such as large-scale remaining gas reserves between wells/layers and low ratio of employed reserves, the main technologies for enhanced gas recovery (EGR) of tight gas reservoirs were developed by multidisciplinary research with respect to development geology, reservoir engineering, drilling and production process, and surface gathering and transportation. Experiments were conducted on reservoir description and remaining gas characterization, well pattern thickening optimization, vertical well separate-layer fracturing, horizontal-well multi-stage multi-cluster volume fracturing for their improvement and upgrading. The orientation of EGR for tight gas reservoirs is proposed. The following results are obtained. First, well pattern thickening optimization is the most important EGR method, which can increase the recovery rate by more than 6%. Second, based on continuous upgrading and promotion, either of reservoir stimulation technology and drainage gas recovery technology can increase the recovery rate by more than 2%. The gathering and transportation technology which further reduces the wellhead pressure can increase the recovery rate by about 1.5%. Third, the EGR technology should be oriented to maximize the quantity of employed reserves, especially by way of new technologies such as fine remaining gas characterization, well pattern/type optimization, cross-layer fracturing of a multi-thin-layer reservoir by horizontal wells, intelligent drainage gas recovery, and multi-stage pressurization. It is concluded that the development of key EGR technologies will help increase the recovery rate of The Sulige Gas Field by 10%–15%, and will provide an effective support for The Sulige Gas Field to maintain the production at 300 × 108 m3/a for a long term and for the Changqing gas province to increase the production to 500 × 108 m3/a, which will ultimately ensure the national energy security.

Comments: Unconventional Shale Reservoirs Meet Cancer Genome Sequencing

The cross-industry development and application of technologies is the epitome of innovation and ingenuity. The more divergent the industries are, the more the unique ways of thinking strike us as remarkable. Technology transfer between the oil and gas industry and other sectors isn’t new. Many examples can be found in medical science, space exploration, and renewable and sustainable technologies. In this JPT issue, the technologies of Oceaneering Space Systems and Impossible Sensing Energy are featured. A case study presented at the 2023 SPE Annual Technical Conference and Exhibition took medical science to a new low—into the depths of the Permian Basin for downhole reservoir drainage diagnostics (RDD). The coauthors, a subsurface and wells manager and a chapter manager, surveillance, analysis, and optimization and pilots at Chevron Technology Ventures (CTV), described using genome sequencing for cancer detection and treatment in a successful proof-of-concept (POC) test conducted from 2017 to 2019. Nampetch Yamali and Daniel Emery explained in SPE 215052 how in 2017 CTV was given the task of identifying technology to assess vertical drainage dimensions to estimate drainage volumes from fractured wells. The goal was to minimize interference from offset wells and co-developments to optimize reservoir recovery in unconventional fields. At that time, the technologies and their capabilities were limited. Although subsurface microbial DNA sequencing for upstream assets has found applications in enhanced biocide and corrosion inhibition, reservoir sweet spot indicators, and tracer technology, use of the technique was thought also to have potential in horizontal well development planning via RDD. Learning of a genomic sequencing technique for cancer cell identification in humans at the biology and biochemistry department at the University of Houston, the wheels started turning at CTV with thoughts it could be developed and adopted for RDD. Similarities were seen because RDD uses in-situ subsurface microbial DNA to infer the depths from which fluids drain after fracturing a horizontal well and optimizes well spacing on a pad, especially in stacked reservoirs. The predictive analytics platform mapped the hydrocarbon footprints of geologic subzones by using noninvasive DNA testing tools. The unique DNA markers for RDD were extracted from mud and cuttings from the horizontal and vertical drilling sections. DNA from produced fluids was also collected. The authors wrote, “Produced fluids collected at two-to-four-week intervals at the wellhead are mapped to the RDD framework. They are ‘lineage traced’ back to shale and tight rock. Drainage heights and percentage of contribution from these locations is computed adapting DNA sequencing and data analytics pipelines which were developed for lineage tracing cancer cells, breaking off from the primary tumor and metastasizing to distant sites back to the tissue of origin.” After validating the DNA extractions, CTV conducted a blind test using only the DNA data to determine the landing zones for each of the four wells in the pad. Using clustering methods, the results of the blind test accurately identified all landing zones within an acceptable margin, according to Yamali and Emery. The next step in the trial analyzed the DNA of the produced fluids. “Preliminary results showed drainage height estimates for each horizontal well.” In 2021, the study continued with an additional four new field trials in the Permian Basin for application of the technique to zonal production identification. The authors wrote, “Although the results from the POC were positive, subsurface DNA RDD technology is a novel technique within the oil and gas industry, and advanced applications are still evolving. This combination naturally gives rise to more general skepticism and a need to thoroughly evaluate the technology from operational, economic, and accuracy perspectives.” The paper describes the ongoing cross-disciplinary work being done by petroleum engineers, geologists, microbiologists, and stratigraphers to fully evaluate this method of RDD. It further details CTV’s wider approach to “accelerate the innovation life cycle, from pilot stages to widespread adoption at scale,” emphasizing the need for leaders’ support for nonconventional thinking and approaches. As the close of 2023 approaches, I’d like to take this opportunity to wish you the best in 2024 on behalf of the JPT Editorial Review Board and the JPT staff. We’ll be kicking off the new year with the commemoration of JPT’s 75th anniversary. Each issue will include an article dedicated to the evolution of technology and industry practices over the seven and a half decades JPT has covered the upstream industry. In January, Trent Jacobs and Stephen Rassenfoss will revisit technological advancements since JPT’s 50th anniversary in 1999. Since then, over 25 million B/D have been added to the global supply thanks in very large part to advancements in drilling, completions, and reservoir technologies. Join us as we explore these along with some predictions made 25 years ago and the surprising realities of where the industry stands today.

Production performance analysis of a continental shale oil reservoir in Bohai Bay basin

Due to the extremely low permeability of shale formations, the combination of horizontal well and volume fracturing has been proposed as an effective technique to improve the production of Dagang continental shale oil reservoirs. Based on the flow material balance method (FMB) and straight-line analysis (SLA) method, the stimulated reservoir volume (SRV) and drainage volume are determined to identify the flow regimes of the seepage mechanism of shale oil reservoirs. To resolve the challenges of multi-scaled flow regimes and bottom hole pressure (BHP) variation before and after pumping in shale oil wells, a multi-linear analytical flow model was established to predict the future production and the final expected ultimate recoverable oil (EURo) after fitting the historical production dynamics. Based on the results, it can be concluded that the flow regime of a shale oil well in production can be divided into two stages consisting of linear flow within SRV and composite flow from the un-stimulated area to SRV. The effects of fracturing operation parameters, such as fracturing fluid volume and sand/liquid ratio, on shale oil productivity, are analyzed, and insightful suggestions are drawn for the future development of this pay zone.

Permeability evolution and production characteristics of inclined coalbed methane reservoirs on the southern margin of the Junggar Basin, Xinjiang, China

The thick and steeply inclined coal seams of the Junggar Basin of Xinjiang, China, are unique with dip angles generally >50° but over the range 0°–85°. Initial and evolving permeability and pressures change drastically around wells down-dip within the steeply inclined reservoir as a result of the depth differential. Hence, the evolution of permeability and fluid pressures during drainage exhibits significant differences from those of flat-lying or even slightly inclined reservoirs. We apply a hydro-mechanical model to evaluate the interaction of two-phase flows of gas and water in the inclined system. The influence of different reservoir inclinations (15°, 30°, 45°, 60°, and 75°) on the evolution of permeability, reservoir pressure, and gas production are explored through finite element modeling of this system. The results show that: 1) Reservoir inclination induces differences in permeability, reservoir pressure, gas content and methane production between the shallower updip reservoir and deeper downdip reservoir. The difference in permeability between the updip and downdip reservoirs is amplified as the dip angle increases and as drainage proceeds in the presence of the varying stress gradient. 2) An apparent asymmetric distribution of reservoir pressures results for wells along dip. The difference in reservoir pressure between the updip and downdip reservoirs intensifies as the inclination increases but lessens with the progress of drainage. The larger the dip angle, the smaller the final reservoir pressure. 3) The pressure reduction in the updip reservoir is larger than that in the downdip reservoir, resulting in the unsynchronized desorption of methane in the updip and downdip reservoirs. Methane within the updip reservoir desorbs preferentially over that in the downdip reservoir. For reservoir dip angles <45° a single peak in methane production rate is apparent but this is supplanted by dual peaks for inclinations >45°. The time gap in gas desorption between the updip and downdip reservoirs results in the “dual-peak” on gas production profile. 4) A larger well spacing along the dip of a more highly inclined reservoir results in more efficient water drainage and gas production. An inverted trapezoidal well pattern is recommended to facilitate the drainage and gas production of reservoirs with significant dip angles.

Fundamentals-Based Alternative Addresses Issue With Three-Phase Permeability Model

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 205883, “Issue With Stone II Three-Phase Permeability Model and a Novel Robust Fundamentals-Based Alternative to It,” by Subodh Gupta, SPE, Heretech Energy. The paper has not been peer reviewed. _ The objective of this paper is to present a fundamentals-based, three-phase flow model consistent with observation that avoids the pitfalls of conventional models. Though the use of the Stone II model is very popular for three-phase flow across the industry, one issue in the context of gravity drainage is how it appears counterintuitively to limit the flow of oil when water is present near its irreducible saturation. The novelty of the work presented in the complete paper is in the development of a model based on fundamentals of flow in fine channels that better explains observed results in the context of flow in porous media. Problem Definition Residual oil saturation (So) from retrieved cores from oil-drained chambers of steam-assisted gravity drainage (SAGD) reservoirs invariably shows values as low as 1 or 2%, whereas reservoir simulations using Stone II-based relative permeabilities (an industrywide favorite) predict significantly higher numbers (14–18%). In previous work, the author and others, in an attempt to remedy the situation, extended the oil-phase relative permeability in the presence of the water phase (krow) and oil-phase relative permeability in the presence of the gas phase (krog) curves all the way to water and gas saturation values less than unity; however, they discovered that, in the presence of water saturation (Sw) near the irreducible water saturation (Swi), the use of the Stone II formula for oil relative permeability still resulted in high residual So. Correct estimation of residual oil-phase saturation is even more important for solvent/steam mixed thermal recovery processes such as solvent-aided processes, where a small amount of solvent is added with steam in SAGD, and significantly more important for solvent-dominated processes, where a small amount of steam or heat is added with a large amount of solvent. A large amount of residual oleic-phase saturation and associated pessimistic solvent-recovery prediction will lead to erroneous economic assessment of these processes. The discrepancy in residual So, as the author and coauthors discovered in previous work, stems from a peculiarity of the Stone II formulation given by Equation 1 of the complete paper. To model this 1D problem numerically, a program developed by the author for his PhD thesis for modeling of moving front reservoir processes with dynamic gridding was modified and run with constant fluid properties for hexane and water at constant pressure and temperature. It also incorporated the three-phase relative permeabilities given by Equation 1 and Table 1 of the complete paper. The results are shown in Fig. 1.

Global Sensitivity Analysis Method for Embankment Dam Slope Stability Considering Seepage–Stress Coupling under Changing Reservoir Water Levels

Ensuring the long-term, efficient, and safe operation of reservoir dams relies on the slope stability of embankment dams. Periodic fluctuations of the reservoir water level due to reservoir scheduling operations make the slope of the reservoir bank vulnerable to instability. To investigate the influence of various factors and their interactions with embankment dam slope stability under changing reservoir water levels, a global sensitivity analysis method is proposed that accounts for seepage–stress coupling. An embankment dam in Shaanxi Province, China, is studied as an example, with COMSOL Multiphysics software simulating the seepage and slope stability of the dam under fluctuating reservoir water level conditions and seepage–stress coupling. The global sensitivity analysis of factors affecting dam slope stability is accomplished by combining Plackett–Burman and Box–Behnken experimental designs, with ANOVA determining the sensitivity of each factor and interaction term. The results demonstrate that during the impoundment period of the reservoir, the saturation line is concave, and the overall stability safety of the dam slope increases first and then tends to be stable, according to the coefficient. The internal friction angle φ, cohesion c, and soil density ρs represent the three most sensitive factors affecting the stability and safety of the dam slope, while c × ρs is a second-order interaction term with significant sensitivity to the stability and safety coefficient of the dam slope. The reservoir drainage period infiltration line is convex, and dam slope stability first reduced and then increased. The magnitude of water level change H, internal friction angle φ, cohesion c, and soil density ρs are the four most sensitive factors for the coefficient of safety of dam slope stability, while c × ρs, H × ρs, and φ × ρs are the second-order interaction terms with significant sensitivity to the coefficient of safety of dam slope stability. These research findings and methods can offer valuable technical support and reference for the investigation and evaluation of the stability of embankment dam slopes.

Simulation of Pipe Networks Using EPANET to Optimize Water Supply: A Case Study for Arjawinangun Area, Indonesia

Abstract In providing clean water services to a community, a clean water supply distribution network system is very important. This study is aimed at the determination of the distribution pipe network by simulating and optimizing the water supply system in the Arjawinangun area, Cirebon, West Java, Indonesia. The data collected was analyzed by using EPANET 2.0 software for modelling water distribution systems. The results show that the total domestic and non-domestic water demand is 391.41 l/s, with a leakage rate of 20%. The pipeline installation plan for the Arjawinangun area is planned to be installed for a length of 23,045 m, with pipe diameters ranging from 400 to 90 mm. The Arjawinangun Area O take Reservoir drainage system, which is at an elevation of +25 m above sea level, requires a distribution pump with a head (H) of 6.0 bar. Also, using the gravity distribution technique, a water tower can be built (~ 55 m) as a water supply booster pump.

Drilling-System Optimization Leads to Expedited Wells Delivery

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202172, “Drilling System Optimization Leads to Expedited Wells Delivery,” by Efe M. Ovwigho, SPE, Saleh Al Marri, and Abdulaziz Al Hajri, Schlumberger. The paper has not been peer reviewed. _ The authors write in the complete paper that simple changes in drillstring design can lead to huge savings in a climate requiring a constant push for reduction in well times and well costs and in improved well delivery. The complete paper explains the process that was followed before implementation of this solution. Introduction To access hydrocarbon reserves in a deep gas field, directional drilling through highly interbedded and abrasive formations was necessary. Designing a fit-for-purpose drilling system for optimal performance was critical. The reservoir drainage strategy required that the development wells be drilled directionally to attain a horizontal displacement of 1,500–2,500 ft at the 7-in. liner point above the gas reservoir formation. The well architecture was designed such that the well would be landed in the 8⅜-in. hole section. This required building inclination from vertical (0°) and landing the well at 80° inclination. Then, 4,000–5,000 ft of a 5⅞-in. hole lateral section would be drilled while holding 80° inclination or occasionally building to 90° inclination. Several initiatives had been implemented with the aim of optimizing drilling performance but had not experienced meaningful success in tackling vibration issues. Design Background An analysis of more than 100 horizontal wells drilled on the project revealed that 35% of total well time was consumed in the 8⅜-in. hole section. The majority of this time was spent on slow drilling or remedial operations. It was imperative that the proposed engineered drillstring meet the following requirements: - Able to drill through highly abrasive and interbedded formations - Maintain stability to avoid or reduce stick/slip, shocks, and vibration - Address surge and swab concerns - Minimize exposure through reduced handling - Optimize torque and drag - Optimized based on available tubulars on the rigsite - Reduce flat time Finite element analysis (FEA) and bottomhole assembly (BHA) modeling was performed with these requirements taken into consideration in a bid to generate a fit-for-purpose BHA (Fig. 1). In the deep gas field where the study was completed, the well had to be landed in the reservoir formation and maintain the 5⅞-in. lateral across the entire pay zone. A critical analysis of the formation determined that compressive strength exceeded 30,000 psi and that the formation was highly abrasive. A complete review of the drilling system was completed to optimize the approach to be taken.

A Mutual Information Theory‐Based Approach for Assessing Uncertainties in Deterministic Multi‐Category Precipitation Forecasts

AbstractThe very nature of weather forecasts and verifications and the way they are used make it impossible for one single or absolute standard of evaluation. However, little research has been conducted on verifying deterministic multi‐category forecasts, which is based on the attribute of uncertainty. The authors propose a new approach using two mutual information theory‐based scores for assessing the comprehensive uncertainty of all categories and the uncertainty for a certain category in deterministic multi‐category precipitation forecasts, respectively. Specifically, the comprehensive uncertainty is defined as the average reduction in uncertainty about the observations resulting from the use of a predictive model to provide all categories forecasts; the uncertainty of a certain category is defined as the reduction in uncertainty about the observations resulting from the use of a predictive model to provide a certain category forecast. By applying the proposed approach and traditional verification methods, the four precipitation forecasting products from the China Meteorological Administration, European Centre for Medium‐Range Weather Forecasts, National Centers for Environmental Prediction, and United Kingdom Meteorological Office were verified in the Dahuofang Reservoir Drainage Basin, China. The results indicate that: (a) the proposed approach can better capture the changing patterns of uncertainties with lead times and distinguish the forecasting performance among different forecast products; (b) the proposed approach is resistant to the extreme bias; (c) the proposed approach needs a careful choice of bin width; and (d) the bias analysis is necessary before verifying the uncertainties in precipitation forecasts.