Reservoir Location Research Articles

CO2–water–rock reaction transport via simulation study of nanoparticles-CO2 flooding and storage

Carbon dioxide (CO2) sequestration for sustainable enhanced oil recovery and reducing greenhouse gas emissions, still faces various challenges. The process performance can improve via injection of nanoparticles into CO2 (NPs-CO2). However, the migration laws of the mixed NPs-CO2 fluid in the reservoir condition, while experiencing a chemical reaction, are still unclear. In this study, a mass transfer model of NPs-CO2 nanofluid is established by combining the migration law of NPs-CO2 fluid and the micro-pore structure change of porous media under CO2–water–rock reaction conditions. Numerical simulation was performed to analyze the CO2 and reservoir formation geochemical reaction via three-dimensional stratigraphic model. Also, the influence of rock microstructure heterogeneity on migration of NPs-CO2 brine fluid and the miscibility were investigated. The physical properties of reservoir were improved as the porosity of the rock increased from 6.43% to 25.84% after 100 years. It was also noted that the average permeability (from 0.013 mD to 0.017 mD) was directly proportional to porosity at various reservoir locations. Results also indicated that due to the CO2–water–rock reaction, porosity, permeability, heterogeneity of the reservoir was generally increasing, which lead to selective migration of NPs-CO2. The local accumulation of NPs-CO2 in detached pores will slightly weaken the original oil displacement efficiency. The density difference between NPs-CO2 and formation water can promote the miscibility of NPs-CO2-brine fluid and can inhibit the acid fluid under buoyancy. The upward diffusion was moved to the cap layer and prevents the chemical reaction of the rocks, that leads to the permanent storage of greenhouse gases.

Radiographic Assessment of Inflatable Penile Prosthesis Reservoir Location Variability in Contemporary Practice

Inflatable penile prosthesis (IPP) reservoirs are typically placed into the Space of Retzius (SOR) or alternative locations including the High Submuscular (HSM) space via transinguinal (TI) or counter incision (CI) techniques. A cadaver study showed variability in reservoir location after TI-HSM placement. To evaluate reservoir location using cross-sectional imaging following IPP insertion. We retrospectively reviewed our institutional database and identified men who underwent virgin penoscrotal IPP insertion between 2007 and 2019. We then identified those men who subsequently underwent cross-sectional imaging prior to October 2019. Radiologists evaluated cross-sectional imaging in a blinded manner and categorized reservoir locations as follows: 1) submuscular; 2) posterior to the external oblique fascia and lateral to the rectus abdominis musculature; 3) preperitoneal; 4) retroperitoneal; 5) intraperitoneal; 6) inguinal canal; 7) subcutaneous. Patients were stratified by reservoir placement technique, transinguinal space of Retzius (TI-SOR), transinguinal high submuscular (TI-HSM), or counterincision high submuscular (CI-HSM). Clinical characteristics and outcomes were reviewed and compared. Statistical analysis was performed using Chi-squared and Fisher's exact tests. Variability exists in the TI placement of SOR and HSM reservoirs, CI-HSM reservoirs were associated with a low level of variability. Among 561 men who underwent virgin IPP insertion during the 12-year study period, 114 had postoperative cross-sectional imaging (29 TI-SOR, 80 TI-HSM, and 5 CI-HSM). Among the 114 patients imaged, TI-HSM reservoirs were more likely than TI-SOR to be located anterior to the transversalis fascia (48 vs 14%, P < .01) and were less likely to be located in the preperitoneal space (18 vs 62%, P < .01). Rates of intraperitoneal reservoir location were similar between the TI-HSM and TI-SOR groups (5 vs 7%, P = .66). Among imaged CI-HSM reservoirs, 4 (80%) were anterior to the transversalis fascia and 1 (20%) was within the inguinal canal. Among all 536 transinguinal cases (131 TI-SOR and 405 TI-HSM), rates of reservoir-related complications requiring operative intervention were similar between groups (5 vs 2%, P = .24). No complications were noted among the 25 patients in the CI-HSM cohort. The level of variability seen in this study did not seem to impact patient safety, complications were rare in all cohorts. This study is the first and largest of its kind in evaluating reservoir positioning in live patients with long-term follow-up. This study is limited in its retrospective and nonrandomized nature. Despite variability with both TI-HSM and TI-SOR techniques, reservoir related complications remain rare. Kavoussi M, Cook G, Nordeck S, et al. Radiographic Assessment of Inflatable Penile Prosthesis Reservoir Location Variability in Contemporary Practice. J Sex Med 2021;18:2039-2044.

KNN-based gas-bearing prediction using local waveform similarity gas-indication attribute — An application to a tight sandstone reservoir

Gas-bearing prediction of tight sandstone reservoirs is significant but challenging due to the relationship between the gas-bearing property and its seismic response being nonlinear and complex. Although machine learning (ML) methods provide potential for solving the issue, the major challenge of ML applications to gas-bearing prediction is that of generating accurate and interpretable intelligent models with limited training sets. The k nearest neighbor ( kNN) method is a supervised ML method classifying an unlabeled sample according to its k neighboring labeled samples. We have introduced a kNN-based gas-bearing prediction method. The method can automatically extract a gas-sensitive attribute called the gas-indication local waveform similarity attribute (GLWSA) combining prestack seismic gathers with interpreted gas-bearing curves. GLWSA uses the local waveform similarity among the predicting samples and the gas-bearing training samples to indicate the existence of an exploitable gas reservoir. GLWSA has simple principles and an explicit geophysical meaning. We use a numerical model and field data to test the effectiveness of our method. The result demonstrates that GLWSA is good at characterizing the reservoir morphology and location qualitatively. When the method applies to the field data, we evaluate the performance with a blind well. The prediction result is consistent with the geologic law of the work area and indicates more details compared to the root-mean-square attribute.

Global investigation of martian sedimentary fan features: Using stratigraphic analysis to study depositional environment

Through the use of high-resolution orbital data, it is possible to study sedimentary fan features on the surface of Mars as archives of past hydrological and climate conditions. Previous studies have commonly interpreted the depositional environment of fan deposits using the geomorphology of the modern fan outcrop alone; however, billions of years of erosion has likely altered the morphology of fan outcrops significantly. Here, we examine the stratigraphy, or internal architecture, of 15 fan deposits across the surface of Mars using orbital outcrop models derived from high-resolution images overlain on digital elevation models. Specifically, we search for a slope break in exposed fan layers, characteristic of a delta deposit and in contrast with an alluvial/fluvial fan that is not expected to have such a slope break. A delta indicates the presence of a downstream standing body of water, providing constraints on the location and abundance of water reservoirs recorded in the sedimentary rock record on Mars. At least one fan outcrop in this study, located in Hargraves crater, shows previously undocumented evidence of a slope break and is thus classified as a delta. Other fan features show some, but not unequivocal evidence of a slope break, but the majority (11) show no evidence of a slope break in their exposed stratigraphy, indicating they cannot be robustly classified as a delta. Of the four fan outcrops with some evidence for deltaic deposition, three are interpreted to have been constructed subsequent to the valley network forming era, including the conclusive delta within Hargraves crater. We also find that all the fan features analyzed in this work have been significantly modified since lithification and have experienced a considerable amount of erosion since initial formation, an important consideration when interpreting the present-day morphology of these landforms on Mars.

Chemical, isotopic and geotectonic relations of the warm and cold waters of the Cotronei (Ponte Coniglio), Bruciarello and Repole thermal areas, (Calabria - Southern Italy)

Geochemical, geological, and hydrological data suggest, for the Cotronei-Caccuri thermal area (Northern Calabria – Southern Italy), the presence of a deep primary geothermal aquifer hosted in the crystalline basement (at Ponte Coniglio) and two secondary aquifers (at Bruciarello and Repole) developed in the Miocene sedimentary succession. Despite the spatial proximity of the three thermal sites, the waters have different compositions: Na(Ca)-Cl for Ponte Coniglio-Cotronei, Na(Ca)-Cl(SO4) for Bruciarello and Na-SO4(Cl) for Repole.The composition of the Cotronei-Ponte Coniglio end-member was reconstructed based on conservative constituents and resulted in a Cl concentration of about 1700 mg kg−1. The thermal waters of Bruciarello and Repole are derived from this primary fluid. Geothermometric calculations support a possible dilution affecting the waters studied to different degrees. For the pure (undiluted) thermal end-member, hosted in the primary granitic aquifer, comparable temperature estimations are provided by cationic geothermometers (67 ± 4 °C) and geothermometric simulations (65 ± 4 °C). However, Bruciarello and Repole waters are in equilibrium with anhydrite and fluorite at a temperature (68.5 ± 4 °C) very similar to that obtained for the granitic aquifer suggesting slight cooling during the travel from the primary granitic aquifer and fast equilibration with anhydrite and fluorite favoured by the rapid dissolution kinetics of these solid phases. From the isotopic point of view, the secondary aquifers have δ34SS(6+) values (+23.01‰ and +22.77‰ ± 0.23‰) comparable with those of the Messinian gypsum (average of +21.8‰). The thermal waters of Cotronei, on the other hand, show enriched δ34SS(6+) values (+38.60‰ ± 0.78‰) due to bacterial reduction of sulfate probably also derived from by Messinian evaporates.Furthermore, the δ18O and δ2H values indicate a meteoric origin for all three thermal sites with an average infiltration altitude of about 1650 – 1850 m asl, which agree with the Sila plateau elevations. Based on the results obtained in this work, assuming a geothermal gradient of about 33 °C/km, a temperature of the deep thermal reservoir of about 65 °C and an average predicted atmospheric temperature of 6 °C in the recharge area (Sila plateau), it follows that the meteoric waters descend to depths of ∼1800 m, where the thermal aquifer of interest is presumably located. This depth is consistent with the location of the primary geothermal reservoir within the crystalline basement. The reconstruction of this conceptual model has been made possible thanks to adopting a "local" approach integrating previously existing and new geological, hydrogeological, and geochemical data. Furthermore, this study has allowed us to identify the presence of an important regional geothermal aquifer hosted in the crystalline basement that, in addition to the carbonate and Upper Triassic evaporite reservoirs (well characterized in previous works), make the Calabria region of high geothermal interest.

H2S observations in young stellar disks in Taurus

Context. Studying gas chemistry in protoplanetary disks is key to understanding the process of planet formation. Sulfur chemistry in particular is poorly understood in interstellar environments, and the location of the main reservoirs remains unknown. Protoplanetary disks in Taurus are ideal targets for studying the evolution of the composition of planet forming systems. Aims. We aim to elucidate the chemical origin of sulfur-bearing molecular emission in protoplanetary disks, with a special focus on H2S emission, and to identify candidate species that could become the main molecular sulfur reservoirs in protoplanetary systems. Methods. We used IRAM 30 m observations of nine gas-rich young stellar objects (YSOs) in Taurus to perform a survey of sulfur-bearing and oxygen-bearing molecular species. In this paper we present our results for the CS 3–2 (ν0 = 146.969 GHz), H2CO 21,1−11,0 (ν0 = 150.498 GHz), and H2S 11,0−10,1 (ν0 = 168.763 GHz) emission lines. Results. We detected H2S emission in four sources out of the nine observed, significantly increasing the number of detections toward YSOs. We also detected H2CO and CS in six out of the nine. We identify a tentative correlation between H2S 11,0−10,1 and H2CO 21,1−11,0 as well as a tentative correlation between H2S 11,0−10,1 and H2O 818−707. By assuming local thermodynamical equilibrium, we computed column densities for the sources in the sample, with N(o-H2S) values ranging between 2.6 × 1012 cm−2 and 1.5 × 1013 cm−2.

Viral, inflammatory, and reservoir characteristics of posttreatment controllers.

To provide an overview of studies to date that have identified posttreatment controllers (PTCs) and to explore current evidence around clinical characteristics, immune effector function, and inflammatory and viral reservoir characteristics that may underlie the control mechanism. PTCs are broadly defined as individuals capable of maintaining control of HIV replication after cessation of antiretroviral therapy (ART). While starting ART early after HIV infection is associated with PTC, genetic disposition or CD8+ T-cell function do not appear to explain this phenomenon, but these features have not been exhaustively analyzed in PTCs. A lower frequency of latently infected cells prior to stopping ART has been associated with achieving PTC, including a lower level of intact HIV DNA, but more studies are needed to map the genetic location, epigenetic characteristics, and tissue distribution of the intact HIV reservoir in PTCs. Current studies are small and heterogeneous and there is a significant need to agree on a uniform definition of PTC. Many aspects of PTC are still unexplored including whether specific features of genetic disposition, immune effector functions, and/or viral reservoir characteristics play a role in PTC. A large multisite international cohort study could aide in providing the important insights needed to fully understand PTC.

Seismic spectral decomposition using short-time fractional Fourier transform spectrograms

A time-frequency method with high resolution is introduced for seismic spectral decomposition. The classical short-time Fourier transform spectrogram has low resolution, limiting its usefulness in application such as stratigraphic visualization and gas reservoir detection for thin beds. This work expands the traditional short-time Fourier transform spectrogram to the fractional domain, leading to the proposed short-time fractional Fourier transform spectrogram (FrFTSG). The short-time Fourier transform spectrogram can be calculated using the 2-D Fourier transform of the product between the ambiguity functions (AF) of the signal and the window function, and using the fractional Fourier transform (FrFT) as the rotation operator of the window function, the window function could be rotated to the direction with the auto-term of the signal in the ambiguity domain. The FrFTSG could be obtained by the 2-D Fourier transform of the product between the ambiguity functions of the rotated window function and the signal. Analyses of synthetic test model and actual seismic data show that the method proposed in this study can characterize the signal with a higher accuracy. This allows more accurate characterization of reservoir location. The method proposed in this paper provides a novel technique for seismic spectral decomposition.

Comparative study of pressure variations in water distribution network due to change in location of elevated service reservoir

This paper compares the pressure variations in a water distribution system due to a change in the location of an elevated service reservoir with an intermittent type of supply for a continuously increasing demand. For this study Water Gems connect edition software is used for the design of a water distribution network. This study is conducted in the Eturnagaram habitation of Mulugu district. The Water Distribution Network is designed for 30 years with PVC as pipe material and intermittent type of supply. Further, this water distribution system is analyzed for pipe bursts and proposes a framework for the operation and maintenance of the water distribution network.

Post‐2018 Caldera Collapse Re‐Inflation Uniquely Constrains Kīlauea's Magmatic System

AbstractFrom August 2018 to May 2019, Kīlauea’s summit exhibited unique, simultaneous, inflation and deflation, apparent in both GPS time series and cumulative InSAR displacement maps. This deformation pattern provides clear evidence that the Halema‘uma‘u (HMM) and South Caldera (SC) reservoirs are distinct. Post‐collapse inflation of the East Rift Zone (ERZ), as captured by InSAR, indicates concurrent magma transfer from the summit reservoirs to the ERZ. We present a physics‐based model that couples pressure‐driven flow between these magma reservoirs to simulate time dependent summit deformation. We take a two‐step approach to quantitatively constrain Kīlauea’s magmatic plumbing system. First, we jointly invert the InSAR displacement maps and GPS offsets for the location and geometry of the summit reservoirs, approximated as spheroidal chambers. We find that HMM reservoir has an aspect ratio of ∼1.8 (prolate) and a depth of ∼2.2 km (below surface). The SC reservoir has an aspect ratio of ∼0.14 (oblate) and a depth of ∼3.6 km. Second, we utilize the flux model to invert GPS time series from 8 summit stations. Results favor a shallow HMM‐ERZ pathway an order of magnitude more hydraulically conductive than the deep SC‐ERZ pathway. Further analysis shows that the HMM‐ERZ pathway is required to explain the deformation time series. Given high‐quality geodetic data, such an approach promises to quantify the connectivity of magmatic pathways between reservoirs in other similar volcanic systems.

Incremental and acceleration production estimation and their effect on optimization of well infill locations in tight gas reservoirs

The main role of infill drilling is either adding incremental reserves to the already existing one by intersecting newly undrained (virgin) regions or accelerating the production from currently depleted areas. Accelerating reserves from increasing drainage in tight formations can be beneficial considering the time value of money and the cost of additional wells. However, the maximum benefit can be realized when infill wells produce mostly incremental recoveries (recoveries from virgin formations). Therefore, the prediction of incremental and accelerated recovery is crucial in field development planning as it helps in the optimization of infill wells with the assurance of long-term economic sustainability of the project. Several approaches are presented in literatures to determine incremental and acceleration recovery and areas for infill drilling. However, the majority of these methods require huge and expensive data; and very time-consuming simulation studies. In this study, two qualitative techniques are proposed for the estimation of incremental and accelerated recovery based upon readily available production data. In the first technique, acceleration and incremental recovery, and thus infill drilling, are predicted from the trend of the cumulative production (Gp) versus square root time function. This approach is more applicable for tight formations considering the long period of transient linear flow. The second technique is based on multi-well Blasingame type curves analysis. This technique appears to best be applied when the production of parent wells reaches the boundary dominated flow (BDF) region before the production start of the successive infill wells. These techniques are important in field development planning as the flow regimes in tight formations change gradually from transient flow (early times) to BDF (late times) as the production continues. Despite different approaches/methods, the field case studies demonstrate that the accurate framework for strategic well planning including prediction of optimum well location is very critical, especially for the realization of the commercial benefit (i.e., increasing and accelerating of reserve or assets) from infilled drilling campaign. Also, the proposed framework and findings of this study provide new insight into infilled drilling campaigns including the importance of better evaluation of infill drilling performance in tight formations, which eventually assist on informed decisions process regarding future development plans.

Volcanic Unrest at Taupō Volcano in 2019: Causes, Mechanisms and Implications

AbstractTaupō volcano, New Zealand, is a large caldera volcano that has been highly active through the Holocene. It most recently erupted ∼1,800 years ago but there have been multiple periods of historic volcanic unrest. We use seismological and geodetic analysis to show that in 2019 Taupō underwent a period of unrest characterized by increased seismic activity through multiple swarms and was accompanied by ground deformation within the caldera. The earthquakes, which include non‐double‐couple events, serve to outline an aseismic zone beneath the most recent eruptive vents. This aseismic zone is coincident with an inflating source, based on forward modeling of ground deformation data. We infer that this aseismic and deforming region delineates the location of the present day magma reservoir that is ≥250 km3 in volume and has a melt fraction of &gt;20%–30%, inhibiting seismic activity. Our analysis shows that the 2019 unrest at Taupō was volcanic in nature and origin, demonstrating that this is an active and potentially hazardous volcano, and that improving our monitoring and understanding of its behavior is important.

An assessment of a shallow geothermal reservoir of Mae Chan hot spring, northern Thailand via magnetotelluric surveys

In a non-volcanic geothermal system, like Mae Chan hot spring and many other hot springs in Thailand, hot water is heated deep underground and seeps to the surface through fractures and faults. Some of the hot water may aggregate in a hydrothermal alteration zone along the fracture zones of granite rocks to form shallow “hot water reservoirs”. These networks lower the bulk resistivity of the granitic rock to form a low resistivity zone associated with the hot water reservoir, which can then be imaged via a magnetotelluric (MT) survey. A series of magnetotelluric surveys from 2013 to 2018 was conducted in order to assess the location, size and depth of the shallow geothermal reservoir of the Mae Chan hot spring. All data were combined to produce the final 3-D resistivity structure. The final MT survey had a high density of MT sites across the zone of interest which allowed us to precisely image the shallow reservoir for drilling purposes. Using the final MT results, five new boreholes with a maximum depth of 200 m were drilled. Hot water was found at various depths from each borehole with perfect agreement with the final resistivity structure derived from the MT data. This 3-D resistivity outline will be useful in developing the field with future production and re-injection wells.

Experimental Study on Blockage Mechanism and Blockage Locations for Polymer-Flooded Reservoirs in the Henan Oilfield

To address the issues of reservoir blockage and sharp decline in fluid output of production wells in the polymer injection zone of the Henan oilfield, physical modeling has been used to study the blockage mechanism and blockage locations of the polymer-flooded reservoir based on oil reservoir characteristics and blockage knowledge. The results show that all the constant pressures in the low, moderate, and high permeability cores subjected to polymer injection and subsequent waterflooding were higher than the constant pressure during primary waterflooding; hence, polymer retention and blockage phenomena were obvious in the cores; in the high permeability core, the pore surface adsorbed more polymer molecules though pore throat radii were still much greater than the size of the polymer molecule, suggesting that polymer blockage is mainly caused by adsorption and retention. For the low permeability core, the specific surface area of the inlet end was much larger than that in the high permeability core, leading to more serious capture of polymer molecules at the small pores, indicating that blockage under polymer injection is mainly caused by capture and retention; for the lower permeability (91.81 mD) core, as compared with the case prior to polymer injection, the polymer-injected core had fewer large pores and throats, the mean pore throat radius decreased from 42.2 μm to 39.9 μm, and the mean throat-to-pore coordination number decreased from 3.36 to 3.19; thus, polymer capture and retention led to core blockage; the leftward shift of the curve corresponding to the porosity component, high porosity peak weakening after polymer injection, moderate and low porosity peaks appearing after polymer injection, and enhancement of lower porosity peaks indicate that, after polymer injection and subsequent waterflooding, polymer adsorption and capture led to blockage of some large pores; the highest pressure gradient, i.e., 6.3 MPa/m, was achieved at the P2-P3 segment; thus, the worst blockage occurred at the P2-P3 stage, or 1/8-1/4 of the sandpack length. In this paper, Nanbaxian oil and gas field, China, was taken as an example to investigate the interpretation method of gas saturation in a complex pore structure. The “four properties” relationship of the formation reservoir in the Nanbaxian oil and gas field was studied in depth according to the conventional logging data and core analysis data. The neural network algorithm was used to reconstruct the resistivity curve of the water layer to eliminate the influence of lithology, shale content, and pore structure on the resistivity. The difference between the reconstructed curve and the measured resistivity curve was used to identify the gas and water, and the ratio of the two was used to calculate the gas saturation, and good results were achieved. It was found that the sedimentary types of the Nanbaxian oil and gas field cause the reservoir to be thin, numerous, and dispersed; the lateral correlation is difficult. In addition, the structural features lead to the reservoir types being various in the vertical direction, which makes the identification of reservoir fluid more difficult. The results revealed that the rock compaction, poor physical properties, complex pore structure, high resistivity of surrounding rocks, and low formation water salinity make the water layer with high resistivity and difficult to identify gas and water.

Sustainable Surface Water Dissolved Oxygen Monitoring at Lake 7/1F, Shah Alam, Selangor

Shah Alam is in Selangor, Malaysia and symbolized with several lakes that are popular among local communities and visitors for leisure and recreational activities. Among of these lakes, few lakes need management to look after its hygienic and well-being to serve its purpose as the recreational lake for the nearby community, such as Lake 7/1F, Shah Alam, Selangor. The secluded location of this water reservoir has made it unpopular, and improper management of it could invite an imbalance environment to its surrounding. Therefore, to initiate the effort, an Internet-of-Thing (IoT) water monitoring system is deployed at this lake to study the dissolved oxygen (DO) level in the water that could indicate the health status of this lake. The system consists of a DO sensor, embedded controller, self-charging power supply, wireless data transmission, and IoT dashboard for in-situ DO measurement. From the analysis, the lake has the normal cycle of DO production, but a dangerous condition is detected when the concentrated DO in the lake water is mostly below the saturation value.

Shadow effect of the pH distribution of surface waters around the Kakkonda geothermal field, Japan

Field surveys were carried out at the Kakkonda geothermal field, where the location of the neutral hydrothermal reservoir has been identified, to investigate the shadow effect of the pH distribution in the actual geothermal development field. Methods using the electrical conductivity (EC)–pH relation and catchment area were employed, and the validity of the data was evaluated to select the most appropriate data for verifying the shadow effect. Results consistent with the concept of a shadow effect were obtained because acidic surface waters strongly affected by volcanic gases were not distributed above the neutral hydrothermal reservoir.

Well Log Analysis of Nahr Umr, Shuaiba and Zubair Formations in EB-4 well of East Baghdad Oil Field, Iraq, using Rock Physics Templates (RPTs)

RPT is a method used for classifying various lithologies and fluids from data of well logging or seismic inversion. Three Formations (Nahr Umr, Shuaiba, and Zubair Formations) were selected in the East Baghdad Oil field within well EB-4 to test the possibility of using this method. First, the interpretations of the well log and Density – Neutron cross plot were used for lithology identification, which showed that Nahr Umr and Zubair formations consist mainly of sandstone and shale, while the Shuaiba Formation consists of carbonate (dolomite and limestone). The study was also able to distinguish between the locations of hydrocarbon reservoirs using RPT. Finally, a polynomial equation was generated from the cross plot domain (AI versus Vp/Vs) to estimate one parameter from the other in these formations, and vice versa.

Calculating the Eroded Thickness Corresponding to a Short-Term Tectonic Uplift with Milankovitch Theory: A Case Study of the Middle Permian Maokou Formation in Southeastern Sichuan Basin, Southwest China.

The Middle Permian Maokou Formation in the southeastern Sichuan Basin is a typical carbonate karst reservoir. At the end of the Middle Permian, a short-term tectonic uplift (Tungwu movement) occurred in the upper Yangtze region, causing the formation of dissolved fissures and holes. To determine the location of the high-quality reservoir, this paper calculated the eroded thickness using the Milankovitch theory. Based on the gamma logging data of the six wells in the southeastern Sichuan Basin, the dominant frequency and the astronomical time scale were evaluated via frequency spectrum analysis, continuous wavelet transform, and empirical mode decomposition. In addition, we analyzed the relationship between Fischer curve characteristics and the variation of lithology. Last, four methods were used to calculate the eroded thickness, and the rationality was analyzed. Consequently, we identified four levels of Milankovitch cycles, i.e., middle eccentricity (e2), short eccentricity (e3), long obliquity (o1), and short obliquity (o2). Also, the Fischer curves of the six wells were divided into two forms related to local structural uplift. The residual strata of the Maokou Formation comprised three complete third-order cycles, and the boundaries were the 15th, 34th, and 54th e3 cycles. The deposition rate of bioclastic limestone was the lowest (2.12–5.36 cm/ka with an average of 3.30 cm/ka), whereas the deposition rate of argillaceous limestone was the largest (2.27–5.25 cm/ka with an average of 4.09 cm/ka). Among the four methods, the missing formation deposition rate method exhibited the most precise calculation results, while that of the seismic data method was relatively low. Generally, the eroded thickness of the Maokou Formation in southeastern Sichuan was in the range of 0–140 m, i.e., the eroded thickness in the west and south of X14 was relatively large (>100 m), while the area north of LS1 experienced the weakest denudation (eroded thickness < 40 m).

Water resource potential at Sekaran Village, Bojonegoro Regency, Indonesia

Water is an essential element for agriculture, including fodder cultivation. The fodder production for School of the Community Farming (SPR) was planned to be located at Sekaran Village, Bojonegoro Regency, Indonesia. Sekaran Village always has water shortage particularly during the dry season. Sekaran Village is located in East Java and the river discharge was low. The study was conducted to evaluate the quantitative potential of water resources from both surface and groundwater. The surface water potential was analyzed based on discharge measurement at the river and rainfall potential at the village. According to river discharge and rainfall potential, several small reservoirs could designed to collect rain water during the wet season and the location for planned reservoir was also examined. Furthermore, the groundwater potential was assessed based on a geoelectrical survey at 20 points of measurements within the study area. The discharge of the river was 1.43 L/sec and of the spring was 0.62 L/sec. The results showed that the groundwater potential was low with only less than 1 L/sec. However, this could be maximized by constructing shallow wells. To choose the reservoir and wells locations, aerial mapping was conducted to portray the topography. The research result could be used by the farmers to design their agricultural activities including developing SPR.

Seismic Velocity Modeling in the Northwest Pearl River Mouth Basin, South China Sea

Accurate seismic velocity can determine the depth, dip angle and location of the stratum, and study the properties of rocks and pore fluid, such as rock density, reservoir location, gas hydrate anomaly and deep tectonic characteristics. The South China Sea (SCS) has special tectonic location and complex evolution history, which has always been the focus of geologists and geophysicists. At the same time, the SCS is rich in oil/gas resources, and is one of the four major marine oil-gas accumulation zones in the world. In this paper, three-dimensional velocity modeling was carried out in northwest Pearl River Mouth Basin of the SCS based on the three-dimensional geological framework model. Minimum Curvature Interpolation was used in the three-dimensional velocity modeling. Results showed that the three-dimensional velocity model can visually display sedimentary boundary and basin basement. The geological framework model makes the lateral velocity change of strata more in line with the actual geological structure. Considering the key role of the underground layer velocity in the exploration of oil, gas, hydrate and lower-crustal structure, it will be of great scientific and resources significance to carry out the three-dimensional velocity modeling research in the SCS.