Case Study of Condensate Dropout Effect in Unconventional Gas/Condensate Reservoirs with Hydraulically Fractured Wells

Condensate banking is a major issue in the production operations of gas condensate reservoirs. Increase in liquid saturation in the near-wellbore zone due to pressure decline below dew point, decreases well deliverability and the produced condensate-gas ratio (CGR). This paper investigates the effects of condensate banking on the deliverability of hydraulically fractured wells producing from ultralow permeability (0.001 to 0.1 mD) gas condensate reservoirs. Cases where condensate dropout occurs over a large volume of the reservoir, not only near the fracture face, were examined by a detailed numerical reservoir simulation. A commercial compositional simulator with local grid refinement (LGR) around the fracture was used to quantify condensate dropout as a result of reservoir pressure decline and its impact on well productivity index (PI). The effects of gas production rate and reservoir permeability were investigated. Numerical simulation results showed a significant change in fluid compositions and relative permeability to gas over a large reservoir volume due to pressure decline during reservoir depletion. Results further illustrated the complications in understanding the PI evolution of hydraulically fractured wells in "unconventional" gas condensate reservoirs and illustrate how to correctly evaluate fracture performance in such a situation. The findings of our study and novel approach help to more accurately predict post-fracture performance. They provide a better understanding of the hydrocarbon phase change not only near the wellbore and fracture, but also deep in the reservoir, which is critical in unconventional gas condensate reservoirs. The optimization of both fracture spacing in horizontal wells and well spacing for vertical well developments can be achieved by improving the ability of production engineers to generate more realistic predictions of gas and condensate production over time.

Integrated Hydraulic Fracturing Strategy Leads to Successful Execution of the First Highly Deviated Ultra-Deep Well in Tarim Oilfield

Well K1002 is the first highly deviated ultra-deep well in Tarim Oilfield of China, with the reservoir depth 7060m and the well deviation of 60° ∼ 77.6° in the fractured interval. Because of large deviation angle, high breakdown pressure and in-situ stress, poor effectiveness of natural fractures, large reservoir thickness, it is difficult and risky to implement hydraulic fracturing. In this paper, the fractured well was taken for a case study to illustrate the holistic optimization to guarantee the treatment success, a world-wide difficulty with high engineering risk. For figuring out a reasonable treatment design, comprehensive lab experiments and numerical simulation were conducted to analyze and benchmark the reservoir characteristics, rock mechanics and geological model. Systematic study on reducing breakdown pressure, development of natural fractures evaluation, multi-size combination of diverting agent, separated layer stimulation and fracture parameters optimization, treatment fluid formulation, proppant screening and operation program were carried out. Considering the wellbore trajectory and rock mechanics characteristics of well K1002, a breakdown pressure prediction model was established to optimize the perforation orientation. The best perforation orientation was 28° and 208°, the worst perforation orientation was 148° and 328°, and the breakdown pressure range was 168-175MPa with 60° phase angle. Combination with "imaging logging (0-3m) + far detection acoustic logging (0-30m) + geomechanics (0-300m)", the comprehensive evaluation and prediction of natural fractures in near wellbore area and far wellbore area were realized. Based on this, the stimulation technology of "mechanical layering + diverting agent" was optimized to connect the fracture development zone in near wellbore and far wellbore area. According to the Tight Packing Theory, the idea of "multi-size particles combination of diverting agent" was put forward. Through the experiment study, the combination of 1-5mm and 5-10mm particles was optimized, and the optimal chart of diverting agent size combination was made under different reservoir temperatures. For the fracturing job, totally 2562m3 KCL weighted fracturing fluid and 159.2m3 ceramic proppant of 40-70 mesh were pumped. The operation parameters were in reasonable agreement with the design. The initial test production was 10 times higher than before. The experience gained in this case study has some guiding significance for improving the success rate of hydraulic fracturing treatments in the highly deviated ultra-deep well and for effectively developing such fractured tight sandstone reservoirs, both theoretically and practically.

Comprehensive sex steroid profiling in multiple tissues reveals novel insights in sex steroid distribution in male mice

A comprehensive atlas of sex steroid distribution in multiple tissues is currently lacking and how circulating and tissue sex steroid levels correlate remains unknown. Here, we adapted and validated a gas chromatography-tandem mass spectrometry method for simultaneous measurement of testosterone (T), dihydrotestosterone (DHT), androstenedione, progesterone (Prog), estradiol, and estrone in mouse tissues. We then mapped the sex steroid pattern in 10 different endocrine, reproductive, and major body compartment tissues and serum of gonadal intact and orchiectomized (ORX) male mice. In gonadal intact males, high levels of DHT were observed in reproductive tissues, but also in white adipose tissue (WAT). A major part of the total body reservoir of androgens (T and DHT) and Prog was found in WAT. Serum levels of androgens and Prog were strongly correlated with corresponding levels in the brain while only modestly correlated with corresponding levels in WAT. After ORX, the levels of active androgens T and DHT decreased markedly while Prog levels in male reproductive tissues increased slightly. In ORX mice, Prog was by far the most abundant sex steroid, and again, WAT constituted the major reservoir of Prog in the body. In conclusion, we present a comprehensive atlas of tissue and serum concentrations of sex hormones in male mice, revealing novel insights in sex steroid distribution. Brain sex steroid levels are well reflected by serum levels and WAT constitutes a large reservoir of sex steroids in male mice. In addition, Prog is the most abundant sex hormone in ORX mice.

Medicinal plants with mosquitoes repellent activity: a systematic review

Repellents are important allies in trying to prevent diseases transmitted by mosquito bites. Plants have been a source of various repellents and insecticides because they have a large reservoir of bioactive substances, in addition, their products have already been tested and are gaining space in research as a low-cost and easy-access alternative. A systematic review was carried out in the databases, Science Direct, Scielo, SciFinder, Springer, PubMed / Medline, Scopus and Web of Science, evaluated by three reviewers. Titles, abstracts and articles were analyzed in full in English, Spanish and Portuguese. To identify the articles, the following descriptors from the Medical Subject Headings (MeSH) were used: “insect repellents”, “essential oils”, “plants extract”, “repellent activity”, mosquitoes and plants. The bibliographic search resulted in 2274 records. Of these, 27 abstracts were considered potentially relevant, and at the end of the selection, 17 articles were included in their entirety. It was found that medicinal plants showed repellent activity against various species of mosquitoes, however due to the little standardization of the methodologies used and the products obtained it is necessary to develop standardized methods to guarantee the quality and reproducibility of clinical trials with medicinal plants.

Vortex profile analysis under different diffuser size for inlet channel of gravitational water vortex power plant

Hydropower is a renewable technology to store the amount of electricity which is the least expensive. Gravitational Water Vortex Power Plant is an ultra-low head micro hydropower system working ranging from 0.7 m to 2m without having the needs of a large reservoir and installation area. Several researches have been conducted on its basin configuration, orifice diameter, blade configuration, the geometry of the basin shape but not onto the addition of the diffuser at the inlet channel. The function of the diffuser is to direct the water into the basin allowing the water vortex to travel towards the tangential direction where this phenomenon will increase the rate of speed flow through the turbine. The simulation results showed that the addition of the diffuser has significantly increased the tangential velocity and the kinetic energy of the vortices. The increase in the velocity of the flow increased the height of the vortex which also led to the increase in the strength of the vortex and affects the vortex uniformity.

Carbonate Platform Reef-Shoal Reservoir Architecture Study and Characteristic Evaluation: A Case of S Field in Turkmenistan

Carbonate sediments are susceptible to many factors, such as paleostructure, diagenesis, and strong microbial alteration; as such, their sedimentary architecture still calls for further research. In this study, the reef and shoal bodies in the XVm and XVp layers of the Middle–Upper Jurassic Karlov-Oxfordian in the S gas field were used as the object, and the architecture of the reef-shoal facies was studied. Based on the idea of “vertical grading and horizontal boundary”, the interface characteristics of the 6th to 4th levels of reef-shoal bodies in the study area were summarized, as were four ways to determine the boundaries of reef-shoal bodies. Based on the dense well network, we quantitatively described the scale of each small layer of single reef shoal body through the point-line-surface method and established a geological database of the reef shoal bodies in the study area. In addition, we established the width and thickness of the reef shoal body and the empirical formula for relationships. The study of morphological characteristics of reef-shoal bodies and the degree of overlap revealed six architecture models of reef-shoal bodies. The vertical and lateral superimposed reefs were obtained by evaluating the reservoir space, pore throat characteristics, and physical property characteristics corresponding to various architecture models. The vertical and lateral superimposed shoals corresponded to large reservoir thicknesses. The petrophysical properties were good, and we concluded that the reef-shoal superimposed area was a sweet spot for reservoir development. We applied the research results of reef-shoal architecture reservoir characteristics to gas field development, and therefore improved well pattern deployment in the reef-shoal superimposed area. By comparing the test results of newly deployed horizontal wells with adjacent vertical wells, we confirmed that the selection of horizontal wells was better for gas field development. This study on the architecture of reef-shoal facies could guide the study of carbonate rock architecture.

Does Fish Conditioning in Aquaculture Increase Survival Success in the Wild? A Case Study on a Cyprinid Fish

Many endangered fish species in the wild are artificially bred, and their populations are strengthened by the stocking of aquaculture-raised juveniles. Because fish from aquaculture are generally not well prepared for the challenging life in the wild, we tested whether training for selected challenges could improve fish survival after stocking. We chose conditioning on predation pressure (by learning predator image of northern pike Esox lucius using predator chemical cues and visual stimuli), increased rearing water velocity 20 cm × s−1, and direct exposure to predation. The juvenile cyprinid fish asp (Leuciscus aspius) was used as a model prey species. A total of 7949 asp were reared in four groups using a combination of high flow, predation, and control treatments (low flow, no predation; 2018, 2149, 1929, and 1856 individuals, respectively). Of these, 1800 individuals were released into three ponds with pike, and their mortality rates were monitored in relation to predation for two months after stocking using passive telemetry arrays. The remaining 6149 aquaculture-reared individuals were released directly into a large reservoir, while 1426 individuals that survived pike predation for two months were released after the pond experiment ended. Fish survival in a reservoir was monitored in 2020 and 2021 by boat electrofishing and passive telemetry. The effect of training in aquaculture was not detected in pond conditions, but the fish that survived direct predation from pike for two months in the semi-natural treatment were more likely to survive in the wild than their aquaculture-reared counterparts. In the laboratory environment, asp responded to predator chemical cues with an increase in shoal cohesion and swimming activity, which demonstrate their ability to detect chemical cues. However, exposure to more fluvial conditions did not result in increased critical swimming speed. The study suggests that conditioning tested in aquaculture may not be sufficient to prepare fish for the wild, while exposing fish to direct predation could increase fish survival.

Diversity and Evolution of Entomocorticium (Russulales, Peniophoraceae), a Genus of Bark Beetle Mutualists Derived from Free-Living, Wood Rotting Peniophora

Symbiosis between insects and fungi arose multiple times during the evolution of both groups, and some of the most biologically diverse and economically important are mutualisms in which the insects cultivate and feed on fungi. Among these are bark beetles, whose ascomycetous cultivars are better known and studied than their frequently-overlooked and poorly understood basidiomycetous partners. In this study, we propose five new species of Entomocorticium, fungal mutualists in the Russulales (Basidiomycota) that are mutualistic symbionts of scolytine beetles. We have isolated these fungi from the beetle mycangia, which are structures adapted for the selective storage and transportation of fungal mutualists. Herein, we present the most complete phylogeny of the closely related genera Entomocorticium and Peniophora and provide insights into how an insect-associated taxon (Entomocorticium) evolved from within a wood-decaying, wind-dispersed lineage (Peniophora). Our results indicate that following a transition from angiosperms to gymnosperms, fungal domestication by beetles facilitated the evolution and diversification of Entomocorticium. We additionally propose four new species: Entomocorticium fibulatum Araújo, Li & Hulcr, sp. nov.; E. belizense Araújo, Li & Hulcr, sp. nov.; E. perryae Araújo, Li & Hulcr, sp. nov.; and E. macrovesiculatum Araújo, Li, Six & Hulcr, sp. nov. Our findings highlight the fact that insect-fungi associations remain an understudied field and that these associations harbor a large reservoir of novel fungal species.

Coastal wave processes numerical modeling for large valley-type reservoirs

The problem of modeling sediment transport and wave processes of large valley-type reservoir under non-stationary conditions of the hydrological cycle active phase (spring-autumn period) is considered. Coupled 2D sediment transport model and 3D wave hydrodynamics was considered to describe these processes, which uses the Navier-Stokes equations. The wave hydrodynamics model is applied to large reservoir of the valley type, such as Tsimlyansky reservoir. Detailed numerical experiments were performed taking into account the real coastline geometry and the bottom relief of the Tsimlyansk reservoir southwestern part. The developed complex of models and programs allows to predict reshaping the bottom relief and coastline under various hydrometeorological conditions. The results of modeling can be in demand when planning water management activities in valley-type reservoirs.

A practical method for planning large number of horizontal wells with a reservoir model for a field development plan

The most advanced technique to evaluate different solutions proposed for a field development plan consists of building a numerical model to simulate the production performance of each alternative. Fields covering hundreds of square kilometres frequently require a large number of wells. There are studies and software concerning optimal planning of vertical wells for the development of a field. However, only few studies cover planning of a large number of horizontal wells seeking full population on a regular pattern. One of the criteria for horizontal well planning is selecting the well positions that have the best reservoir properties and certain standoffs from oil/water contact. The wells are then ranked according to their performances. Other criteria include the geometry and spacing of the wells. Placing hundreds of well individually according to these criteria is highly time consuming and can become impossible under time restraints. A method for planning a large number of horizontal wells in a regular pattern in a simulation model significantly reduces the time required for a reservoir production forecast using simulation software. The proposed method is implemented by a computer script and takes into account not only the aforementioned criteria, but also new well requirements concerning existing wells, development area boundaries, and reservoir geological structure features. Some of the conclusions drawn from a study on this method are (1) the new method saves a significant amount of working hours and avoids human errors, especially when many development scenarios need to be considered; (2) a large reservoir with hundreds of wells may have infinite possible solutions, and this approach has the aim of giving the most significant one; and (3) a horizontal well planning module would be a useful tool for commercial simulation software to ease engineers' tasks.