Loose Sandstone Research Articles

RETRACTED ARTICLE: Stress Sensitivity of Loose Sandstone and Sports Training Management Based on Image Recognition

This paper studies the stress sensitivity and training management of loose sandstone based on image recognition in detail. Loose sandstone is one of the most common storage rocks, which accounts for a large proportion at home and abroad. In the process of developing loose sandstone reservoir, it is basic to obtain the mechanical parameters correctly. Because of the high porosity, high permeability and weak separation strength of loose sandstone, the paper discusses the influence of gap water pressure, and temperature on mechanical parameters of loose sandstone. The compressive strength of loose sandstone decreases with the increase of the gap water pressure. The elastic modulus of loose sandstone will decrease greatly under low clearance water pressure, but it is slow to decrease under high clearance water pressure, and Poisson ratio will decrease first and then increase. But the accuracy of quadratic fitting of compression strength, elastic modulus, and clearance water pressure is high, but the accuracy of Poisson ratio is low and the correlation is weak, which shows that there is no accurate correlation between Poisson ratio and clearance water pressure. With the increase of temperature, the compressive strength, and elastic modulus of loose sandstone begin to decrease, then rise, and then decrease rapidly after reaching the critical temperature. This is not good for the stability of the rock. Based on the above research, the general university physical education outside the curriculum is finally fully understood, which provides the basis for the decision-making and proposal of relevant departments. This paper uses literature, questionnaire, interview, mathematics statistics, logical analysis, and other methods to take 93 universities as the subjects of investigation. This paper investigates the status of university administration, coaches, athletes, and stadiums, and then uses SPSS12.0 system and Excel software to make statistics and processing of data, so as to provide strategies for sports training management.

A new type of low density cement slurry suitable for sandstone formation

Unconsolidated sandstone reservoir is an important unconventional oil and gas resource with the characteristics of porosity, low permeability, strong heterogeneity and many interlayer. The main challenge of unconsolidated sandstone formation is sand production of oil wells, and the more serious situation is high-pressure oil and gas escaping, blowout accidents, environmental pollution and the safety of operators. In order to solve the sensitivity problem of loose sandstone, a low density admixture was developed: 10.5% artificial floating bead + 4.5% power plant floating bead + 35% micro silicon + 30% fly ash + 20% slag. The particle size distribution of single lightweight material is narrow, and the effect of reducing density is not significant. The developed low-density mixing material has wide and uniform particle size distribution, and can reduce the density of cement slurry to the maximum within the minimum dosage. The new low density admixture cement slurry with adjustable density in the range of 1.4 ∼ 1.7 g / cm3 has good rheological property, short thickening time, water loss less than 50 ml, 24 h compressive strength more than 12 MPa, which can meet the needs of site construction. The temperature and pressure test results show that the system has a wide range of temperature and pressure applications and stable performance. Compared with the similar low density cement slurry, it is about 40% lower than the market price and suitable for commercial application.

Cenozoic Stratigraphy of the Eastern Part of the Opukha–Pekulney Depression, Koryak Upland, Northeast Russia

The Cenozoic marine deposits (two formations) developed in the eastern part of the Opukha–Pekulney Depression of the Koryak Upland are described. Until recently, there was scarce information about them. The lower (Retyrveem) formation is composed of dark conglomerates and sandstones with a large number of carbonate nodules and representative assemblages of bivalve and gastropod mollusks (more than 400 tests and imprints were studied) and Early Eocene benthic foraminifers. Two subformations and six units were distinguished in the formation. The upper (Morzhovaya) formation is composed of light loose gravestones and sandstones, including fragments of Early Miocene mollusks and foraminifers. The study of faunal assemblages makes it possible to correlate these formations with stratigraphic units of adjacent areas and to reveal hiatuses in the section covering most of the Paleocene sequence, on one hand, and the Upper Eocene and Oligocene, on the other hand. The Retyrveem Formation encloses warm-water molluscan assemblages, the appearance of which in the northern boreal latitudes is supposed to be related to the Early Eocene global warming. Images of the characteristic molluscan remains are given for the first time.

Annular Ledge Formation Method Allows Sidetracking in Multilateral Wells

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 19350, “Effective Annular Ledge Formation Sidetracking in Multilateral Wells in the Vostochno-Messoyakhskoye Field,” by Andrey Voronin, Messoyakhaneftegaz, and Nikolay Abaltusov, SPE, and Anton Vershinin, Weatherford, et al., prepared for the 2019 International Petroleum Technology Conference, Beijing, 26–28 March. The paper has not been peer reviewed. Copyright 2019 International Petroleum Technology Conference. Reproduced by permission. Multilateral drilling technology offers a highly effective method of enhanced oil recovery in fields characterized by complicated geological structures. This paper describes the analysis of sidetracks drilled in an open hole by an annular ledge formation method with a downhole motor in multilateral wells. Introduction Currently, industry growth requires development of fields with complicated geology. Drilling single-bore horizontal holes for these fields is insufficient, to say nothing of drilling vertical or directional wells. Multilateral wells with multiple horizontal sidetracks are drilled with increasing frequency. The competition between downhole motors and rotary steerable systems (RSS) in multilateral-well drilling is fierce. In the complete paper, the authors describe deployment of a method previously only available with RSS that provides advantages to downhole-motor use: annular ledge formation, which involves sidetracking in an open hole. In the case study described, a conventional motor is used without additional electronics. Conventional sidetracking methods in an open hole with the use of motors involve sliding. During sidetracking, the sliding is aggravated additionally by a low rate of drillstring movement. If side-tracking with the conventional method is impossible, then usually a special sidetracking bit is installed and the motor-bend angle is increased. Such measures result in additional time and financial expenditure. The annular ledge formation method allows for sidetracking in an open hole with the use of a standard bottomhole assembly (BHA) with a motor, which also will be used for drilling a lateral. The key feature of this method lies in the fact that, during sidetracking, the drillstring is constantly rotating, which allows avoidance of the problems related to sliding. When sidetracking with the use of this method, the ledge is formed over the entire circumference of the borehole, not only on the bottom wall. But, when sidetracking deeper, a trough is formed on the low side of the hole and the upper side remains unaffected. Because of this, the annular ledge formation method is described by the authors as sidetrack with rotation. The authors discuss the deployment of this method in the Vostochno-Messoyakhskoye field when drilling multilateral fishbone wells. The complete paper presents a detailed discussion of the method and different situational approaches to its use. Vostochno-Messoyakhskoye Field The field is the northernmost developed onshore oil field in Russia in the Tazovsky region 250 km from the Arctic Circle in the Arctic climatic zone. The field is developed with horizontal production and injection wells along a horizontal section length of approximately 1000 m. The geology of the reservoirs is complicated with a large gas cap. In terms of geological conditions, the PK 1-3 pay zone is irregular within the field and is represented by loose sandstones both uniform and horizontally layered. The oil-bearing formations are isolated.

Geothermal sources and utilization practice in six countries along the southern part of the Pannonian basin

Data on thermal water sources with outflow temperature of 30 °C and above were analyzed from the N-ern parts of Bosnia and Herzegovina, Serbia and Croatia, S-ern parts of Hungary, W-ern parts of Romania, and NE-ern parts of Slovenia, altogether from an area of 99,347 km2. The overview identified 771 geothermal sources; only 7 were thermal springs. The average well depth is about 1.2 km. About 13% of wells are younger than 10 years, additional 17% below 30 years; while 26% are older than 50 years. Average thermal water outflow temperature is 54 °C being the highest, 170 °C, in Croatia. Most thermal water is produced from basin fill sediments—Lower and Upper Pannonian (Mio-Pliocene) loose sandstones which are tapped by 86% of wells. The rest appertains to basement rocks—fissured, fractured and karstified Paleozoic, Mesozoic and Middle Miocene metamorphic, carbonate and siliciclastic rocks. In total, 72% sources hold water rights, 6% mining rights, 2% geothermal rights and 1% has no rights. The permits allow much higher water abstraction as currently listed. Usage for bathing and balneology encompasses 24% of all active sources (155), some of these also with heating (23). 104 objects (16%) are used for heating, also district heating (13) and individual space heating (3). An additional 10% (70) are used in agriculture, mainly greenhouse heating. There are 41 reinjection wells (5%). It is primarily in Hungary that drinking water (17%), industrial usage (5%) and monitoring wells (2%) are also common.

Fabrication and Evaluation of Weakly Cemented Three-dimensional Large-size Loose Sandstone Core

In order to realize the three-dimensional physical simulation experiment of loose sandstone reservoirs, one of the key points lies in how to obtain the three-dimensional large-size cores that can represent the actual reservoir conditions. However, due to the characteristics of small cementation strength, easy to loose, the large-scale cores drilling on site are difficult to achieve, so the preparation of weakly cemented three-dimensional large-scale loose sandstone cores is proposed. Through the design of the core mold, based on the particle size group and physical parameters of the target reservoir, and considering the macroscopic characteristics such as the actual reservoir thickness and the shale interlayer, weakly cemented three-dimensional large-scale core and saturated probe core are used. The physical properties of formed cores are evaluated and tested. The results show that compared with the actual reservoir, the porosity and permeability error of the core model is kept at about 10%, the precision is high, the homogeneity in the layer is good, the average cementation index of each layer is 1.6, which is a weak cementation category, and the degree of cementation consistent with the target reservoir. The prepared core can be done well in reducing the physical properties and macroscopic structure of the actual reservoir, and provides reliable core source support for the three-dimensional physical simulation experiment of the loose sandstone reservoir.

Cracking Mode Analysis of Crack Initiation in Rocks under Uniaxial Compression

Crack initiation is related to the behavior of the preexisting microcracks within a rock specimen, which suggests the specimen starts to fail. The determination of crack initiation stress is important for identifying the elastic stage and related mechanical parameters. Uniaxial compression tests with acoustic emission monitoring were performed to study crack initiation for tight sandstone, loose sandstone, and granite. The evolution of the cracking mode, i.e., the statistics of the cracking mode under compression, was obtained through modified acoustic emission parameter analysis. Based on the logarithm of the acoustic emission parameter (LAEP), a cracking mode analysis (CMA) method is proposed and used to determine the crack initiation stress. Results from the tests indicate that the crack initiation stress between the same rock specimens obtained by CMA is very close. The mean ratio of crack initiation stress to compression strength is 0.45, 0.34, and 0.35 for tight sandstone, loose sandstone, and granite, respectively. According to the results of CMA, crack volumetric strain (CVS) method, and lateral strain response (LSR) method, there is no big difference among those methods in tight sandstone and loose sandstone. In granite, the results obtained by CMA are close to those obtained by CVS, but smaller than those obtained by LSR. The CMA interprets the initiation of cracks from the fracture behavior of microcracks and is an objective method to determine the initiation stress.

Evaluation of the Percolation Sensitivity of Loose Sandstone Using Digital Core Technology

Background:The integrity of the extracted core in loose sandstone gas reservoirs is poor, and because hydration and collapse easily occur, it is difficult to evaluate the sensitivity characteristics accurately by the traditional core flooding experiments.Objectives:We instead investigate the stress sensitivity and water sensitivity of the formation water soaking time using digital core technology.Methods:We take the core of a loose sandstone gas reservoir as a research object and begin by scanning the core samples with a CT scanner. A three-dimensional image of the core can be obtained, the digital information extracted, the pore structure of the porous media mapped directly to the network, and a digital core established using the principles of fractal geometry. The three-dimensional pore network model can also be extracted. Next, we can compare and correct the results calculated by the model based on the real core experimental results, and an objective and effective digital core model can be obtained.Results and Conclusion:Finally, we can calculate the different effective stress, pore throat parameters (pore throat radius, shape factor, coordination number, pore-throat ratio) and relative permeability of different formation water injury times. The research results demonstrate that in sandstone gas reservoir development, as the effective stress continuously increases, the rock pore-throat parameters continue to decrease, and the permeability of the reservoir rock ultimately declines by more than 43.2%. Clay minerals will expand after the edge and bottom water intrude into the reservoir and soak it for a long time: the pore throat is significantly narrowed within 30 days, while after 30 days more, the pore throat undergoes any only slight further changes, and the final permeability decline of the reservoir rock is up to 5.7%. The research results provide important basic petrophysical data for the development of loose sandstone gas reservoirs which, in turn, provide a scientific basis for formulating a reasonable gas production rate in a gas reservoir.

The variation mechanism of petrophysical properties and the effect of compaction on the relative permeability of an unconsolidated sandstone reservoir

Abstract This study investigated the influence of compaction on the variation mechanism of petrophysical properties and the relative permeability of unconsolidated sandstone. Firstly, triaxial mechanical experiments, CT scans, and mercury injection experiments were performed to analyze the microstructural characteristics and the macroscopic mechanism of changes in the petrophysical characteristics under different pressure. Secondly, a modified permeability test approach was adopted on reservoir cores in which a constant flow rate was maintained by changing the pore fluid pressure. The factors which affect the porosity and permeability of unconsolidated sandstone under compaction were investigated. Finally, two-phase displacement tests were performed to assess the influence of compaction on oil production. The results demonstrate that the porosity, permeability, and pore-throat size of loose sandstone are reduced with increasing compaction. Although the relative rigidity of the grains makes the reduction in porosity comparatively smaller, the permeability shows a sharp decline and the change is irreversible. The irreducible water saturation and residual oil saturation increase and the position of two-phase flow zone narrows with decreasing porosity and permeability. These changes act to weaken the percolation flow capacity and lead to a decline in oil-well productivity in areas where water injection is not timely or is insufficient. The understanding of compaction mechanism can be used to optimize the development of compacting reservoirs to take advantage of the compaction.

DETERMINATION OF POROSITY IN SEMI-CONSOLIDATED AND LOOSE ROCKS

Formulation of the problem. Due to the fact that the volume of drilling in the shallow horizons of the Mesozoic has recently been increased, the collectors are more often selected in the core with weakly cemented and loose sands and sandstones. Weak consolidation of rocks makes them difficult to study because of the impossibility of using standard, commonly used techniques. As a result, an interest in the methodological part of determining the collecting properties of such rocks became aggravated.The aim of this work is to choose the most reasonable method of porosity determination of the semi-consolidated and friable rocks and its mastering to the operative complex of researches.The basic content. The article considers the methods of determining the porosity used in engineering Geology and total porosity of the bulk rocks using the Remniov’s formula. The latter provides pre-compaction of samples under a pressure similar to the effective pressure on the sample and has a few options. The device for pre-consolidation and the method of its application have been developed. Ways to determine the values of effective pressure during compaction have been considered.Conclusions. On the basis of the work final conclusions have been formulated according to the declared purpose of the work:1. As long as it is technically possible, within the operational complex for determining porosity of semi-consolidated rocks it is better to use a standard saturation method.2. In other cases on semi-consolidated and always on friable rocks it is needed to use the method of the direct measuring on a model, under effective pressure, calculation on a formula {3}, where rock pressure is calculation on the formula of Р=γh. Porosity should be calculated on a formula {2} with the use of quartz specific gravity.

Erratum to: Hydrogeochemical and isotopic tracers for identification of seasonal and long-term over-exploitation of the Pleistocene thermal waters

The aim of the study was to develop and test an optimal and cost-effective regional quality monitoring system in depleted transboundary low-temperature Neogene geothermal aquifers in the west Pannonian basin. Potential tracers for identification of seasonal and long-term quality changes of the Pleistocene thermal waters were investigated at four multiple-screened wells some 720 to 1570 m deep in Slovenia. These thermal waters are of great balneological value owing to their curative effects and were sampled monthly between February 2014 and January 2015. Linear correlation and regression analyses, ANOVA and Kolmogorov–Smirnov two-sample test for two independent samples were used to determine their seasonal and long-term differences. Temperature, pH, electrical conductivity, redox potential and dissolved oxygen did not identify varying inflow conditions; however, they provided sufficient information to distinguish between the four end-members. Characteristic (sodium) and conservative (chloride) tracers outlined long-term trends in changes in quality but could not differentiate between the seasons. Stable isotopes of δ 18O and δ 2H were used to identify sequential monthly and long-term trends, and origin and mixing of waters, but failed to distinguish the difference between the seasons. A new local paleo-meteoric water line (δ 2H = 9.2*δ 18O + 26.3) was outlined for the active regional groundwater flow system in the Pannonian to Pliocene loose sandstone and gravel. A new regression line (δ 2H = 2.3*δ 18O–45.2) was calculated for thermomineral water from the more isolated Badenian to Lower Pannonian turbiditic sandstone, indicating dilution of formation water. Water composition was generally stable over the 1-year period, but long-term trends indicate that changes in quality occur, implying deterioration of the aquifers status.

Mitigating depletion of a porous geothermal aquifer in the Pannonian sedimentary basin

This paper investigates depletion rates and available thermal water resources of the transboundary Upper Pannonian loose sandstone geothermal aquifer of the Mura Formation in the Mura-Zala sedimentary basin in north-eastern Slovenia, and outlines a regional reinjection strategy to mitigate depletion. The research monitoring network of 12 geothermal wells, which is being constantly upgraded since 2009, has highlighted that the current abstraction rate of 2.4 million m3 in 2014 is not sustainable because hydraulic state has been continuously deteriorating regionally while the chemical state is affected only locally. The average regional drawdown rate in observation wells is 0.67 m annually, while very rough average value for abstraction wells is 3.0 m per year. The cumulative historical regional drawdown is above 16 m. The available thermal water resources are addressed as the cumulative abstraction rate which reverses the observed declining trend of groundwater levels, and were numerically assessed to be ~1.3 million m3 of thermal water per year. These numerical models set up in the AUTOUGH2 code also provided the quantification tool of the regional groundwater balance and confirmed the gravity-driven regional groundwater flow with prevailing conductive heat transfer mechanism. Simulations of the regional reinjection strategy outline that the cumulative reinjection rate of ~1.48 million m3 of thermal water per year should be sufficient to reach good status of the aquifer if the cumulative regional abstraction rate does not change. If it does, the rate should be adjusted accordingly. The water is provided by eight users of geothermal heat and should be returned by the existing reinjection wells in Lendava and Murska Sobota and two new wells situated in the central part of the basin by 2021 the latest. These findings should enhance optimization of exploitation practice and implementation of geothermal doublets in the region as the successful example of a doublet in Lendava exemplifies that no major technological issues should occur if the system is properly designed.

Hydrogeochemical and isotopic tracers for identification of seasonal and long-term over-exploitation of the Pleistocene thermal waters.

The aim of the study was to develop and test an optimal and cost-effective regional quality monitoring system in depleted transboundary low-temperature Neogene geothermal aquifers in the west Pannonian basin. Potential tracers for identification of seasonal and long-term quality changes of the Pleistocene thermal waters were investigated at four multiple-screened wells some 720 to 1570m deep in Slovenia. These thermal waters are of great balneological value owing to their curative effects and were sampled monthly between February 2014 and January 2015. Linear correlation and regression analyses, ANOVA and Kolmogorov-Smirnov two-sample test for two independent samples were used to determine their seasonal and long-term differences. Temperature, pH, electrical conductivity, redox potential and dissolved oxygen did not identify varying inflow conditions; however, they provided sufficient information to distinguish between the four end-members. Characteristic (sodium) and conservative (chloride) tracers outlined long-term trends in changes in quality but could not differentiate between the seasons. Stable isotopes of δ (18)O and δ (2)H were used to identify sequential monthly and long-term trends, and origin and mixing of waters, but failed to distinguish the difference between the seasons. A new local paleo-meteoric water line (δ (2)H = 9.2*δ (18)O + 26.3) was outlined for the active regional groundwater flow system in the Pannonian to Pliocene loose sandstone and gravel. A new regression line (δ (2)H = 2.3*δ (18)O-45.2) was calculated for thermomineral water from the more isolated Badenian to Lower Pannonian turbiditic sandstone, indicating dilution of formation water. Water composition was generally stable over the 1-year period, but long-term trends indicate that changes in quality occur, implying deterioration of the aquifers status.

Simulating the stabilization effect of soil bioengineering interventions in Mediterranean environments using limit equilibrium stability models and combinations of plant species

One of the critical problems in projecting soil bioengineering interventions is the difficulty in developing precise calculations of the evolution of the structures and the type and combination of vegetation plantations that are planned for the particular site and problem. This is mainly due to the uncertainties in the plant development in each type of soil, the long and short term weather patterns and other edapho-climatic factors that determine limited calculation possibilities causing considerable degrees of uncertainty. This leads to a reduced level of reliability of bioengineering projects in terms of pre-determined factors of safety. In Mediterranean conditions this problem is even stronger due to the high seasonal and year-to-year climatic variability, and high degree of uncertainty in the vegetation installment and growth patterns.To evaluate the comparative short and long term (up to 20 years) efficacy of the most used slope stabilization techniques, common calculation models were used to assess the factor of safety of those techniques. SLIP4EX was used to evaluate the factor of safety, while the normal Coulomb model was used to assess the resistance to sliding and overturning. Considering the average Mediterranean climatic conditions, the considered environmental conditions were the least favorable, in order to assess the reliability of the “worst case scenario”. Two common tree species in the western Mediterranean region (Pinus halepensis and Quercus faginea) were selected for the simulation and three common soil types were considered (stony clay, loose sandstone and sandy marl).The results of the simulations for different types of substrates, plant combinations and designs, show that, according to the modeling approaches, the use of soil bioengineering techniques, present a reliable effectiveness, confirmed by the experience gathered in interventions in Mediterranean sites with similar edapho-climatic conditions.Additionally, because bioengineering is about the factor of safety of the target vegetation after the decay of the combined structure, the efficiency as a slope support structure of a vegetated log cribwall was compared with the expected developed vegetation. It was concluded that an adequate development of the vegetation ensures all safety requirements even in the worst considered scenarios.Our results also illustrate that there is a generalized lack of data on the geotechnical characteristics of the Mediterranean vegetation, which is particularly critical in a geo-ecological context where bioengineering techniques face important limitations (very few species able of vegetative development of roots and shoots from live cuttings).

Generalization of the Expression of Cementation Radius in Contact Cement Theory and Its Application

AbstractThe general expressions of cementation radius in the loose sandstone are proposed on the basis of the geometry relationship between the grain and cement with the assumption that the contact thickness is not zero. The expressions of cementation radius of Contact Cement Theory (CCT) proposed by Dvorkin et al. (1996) don't consider the effect of contact thickness, which makes it only applicable for the pore cemented loose sandstone. To solve this problem, the general expressions of cementation radius are proposed, in which the effect of contact thickness on the velocity of loose sandstone is analyzed. And its application in the prediction of the compressional and shear wave velocity of basally cemented loose sandstone is discussed. The results show that when the contact thickness increases, the compressional and shear wave velocities decrease. Such trend is more obvious when the porosity increases or the content of cement decreases. The ratio of compressional wave velocity to the velocity of shear wave (Vp/Vs) increases with the contact thickness if the porosity or cement content keeps stable. Vp/Vs changes with porosity in different ways for different contact thicknesses. When the thickness is small, the ratio decreases a little with the increase of porosity, but when the thickness becomes large, it changes in the other way. For the basally cemented loose sandstone, the modified model using the general expression of cementation radius predicts both the compressional and the shear wave velocities better than the original CCT. The study also shows that the change of the rigidity of the basally cemented loose sandstone caused by porosity or cement content change cannot be predicted by Vp/Vs, but it can predict that caused by the change of contact thickness.

The effect of rock electrical parameters on the calculation of reservoir saturation

The error in calculating a reservoir saturation caused by the error in the cementation exponent, m, and the saturation exponent, n, should be analysed. In addition, the influence of m and n on the reservoir saturation should be discussed. Based on the Archie formula, the effect of variables m and n on the reservoir saturation is analysed, while the formula for the error in calculating the reservoir saturation, caused by the error in m and n, is deduced, and the main factors affecting the error in reservoir saturation are illustrated. According to the physical meaning of m and n, it can be interpreted that they are two independent parameters, i.e., there is no connection between m and n. When m and n have the same error, the impact of the variables on the calculation of the reservoir saturation should be compared. Therefore, when the errors of m and n are respectively equal to 0.2, 0.4 and 0.6, the distribution range of the errors in calculating the reservoir saturation is analysed. However, in most cases, the error of m and n is about 0.2. When the error of m is 0.2, the error in calculating the reservoir saturation ranges from 0% to 35%. Meanwhile, when the error in n is 0.2, the error in calculating the reservoir saturation is almost always below 5%. On the basis of loose sandstone, medium sandstone, tight sandstone, conglomerate, tuff, breccia, basalt, andesite, dacite and rhyolite, this paper first analyses the distribution range and change amplitude of m and n. Second, the impact of m and n on the calculation of reservoir saturation is elaborated upon. With regard to each lithology, the distribution range and change amplitude of m are greater than those of n. Therefore, compared with n, the effect of m on the reservoir saturation is stronger. The influence of m and n on the reservoir saturation is determined, and the error in calculating the reservoir saturation caused by the error of m and n is calculated. This is theoretically and practically significant for the precise calculation of the saturation of complex reservoirs.

Expansion Slurry System Research

In-depth development of a block of Sudan, effectively develop the rich reserves of the major reservoirs, increase crude oil production, and reduce the cost of drilling.This horizon has a high penetration, high formation temperature, easy to collapse, gas channeling and complex problem, there is a great test of this case to horizontal wells cementing.Therefore, develop a new expansion slurry system,which has the feature of high-strength, low water loss, gas channeling effect, solves the region problems of cementing technical. A block of Sudan formation pressure coefficient is low, fracture pressure is small, strata is sulfur loose sandstone, and stratigraphic diagenetic is poor, easy to collapse and necking.With the deepening of the development ,these issues are more and more obvious.In order to achieve the best results in the horizontal well cementing operations, we research from geological data, well structure, cementing formulations and process in-depth and meticulous. Solve the high permeability formation temperature, easy to collapse, gas channeling technical problems, develope a new type of high-strength, low water loss, micro-expansion slurry system, and effectively solve the block problem of horizontal wells cementing .

Mechanical Analyze of Casing Failure with Sand Production in Loose Sandstone Reservoir

Sand and fluid may both run into the wellbore during the production of loose sandstone reservoir, but cavities around the wellbore are prone to form when sand is produced, which makes the casing lost the protection of the formation and casing failure comes about. The limitation of thin cylindrical shell buckling model is analyzed and a mechanical model for casing under sand production is established by M.M.протодьяконоВ’ theory and the pressures of the casing where cavities exist are determined by numerical method. The research shows the cavity height and sand production volume are in a power relationship; the cavity height and axial force are in a linear relationship. With the increase of the overburden pressure, higher steel grade have to be used to keep the reliability of the casing. The research provides theoretical foundation for production casing design and casing strength verification with reasonable sanding.

Paleoenvironment of Deposition of the Dupi Tila Formation, Lalmai Hills, Comilla, Bangladesh

Abstract The Dupi Tila Formation is composed of yellow to light brown medium to very fine moderately hard to loose sandstone, siltstone, silty clay, mudstone and shale with some conglomerates with clasts of petrified wood. The lithofacies of matrix supported conglomerate, trough cross bedded conglomerate, massive sandstone, trough cross bedded sandstone, planar cross bedded sandstone, ripple cross laminated sandstone-siltstone, flaser laminated sandstone-shale, lenticular laminated sandstone-siltstone-shale, parallel laminated sandstone-siltstone, wavy laminated shale, parallel laminated blue shale, and mudstone are delineated within this formation. Based on the grain size, sedimentary structures, water depth and genesis of individual facies, facies are grouped into three types of facies associations like (i) coarse-grained conglomerate facies association in relation to tractive current deposits of alluvial fan set up at the base of litho-succession (FAC), (ii) medium to fine-grained sandstone-siltstone-mudstone facies association or facies association in relation to strong tide (FAT) characterizing the middle part of litho-succession, (iii) very fine-grained sandstone-siltstone-mudstone facies association in relation to less frequent weak tide or heterolithic facies association (FAHL) characterizing upper part of litho-succession and shallow marine facies association (FASM) composing the uppermost litho-succession. Presence of gluconite indicates that the depositional environment was shallow to deep marine. The dominant paleoflow direction during the deposition of Dupi Tila Formation was toward southeast to southwestern direction. The rivers were of braided type at the piedmont alluvial depositional set up at the lower part, which later changed to estuarine–tidal flat type environmental set up in the middle part to upper part and paleo-environment was shallow marine in the uppermost part.

Combining seismic and electric methods for predicting bedrock depth along a Mediterranean soil toposequence

Bedrock depth provides important information for many environmental and agricultural applications, such as shallow groundwater monitoring, the determination of soil water availability, and the estimation of crop production potential. Direct estimates of bedrock depth from destructive soil observations are discontinuous and too expensive to be used in large areas. Geophysical methods are often cited as possible alternatives. However, their ability to provide reliable estimations of bedrock depth is known to depend greatly on local site characteristics. Therefore, combining geophysical methods based on different physical parameters may help to provide better predictions. This study examines the ability of the Spectral Analysis of Surface Waves (SASW) method combined with the classical high resolution Electrical Resistivity Tomography (ERT) method to predict soil depths in a 500m ranged Mediterranean hillslope (Southern France) with increasing soil depths along the slope. SASW was performed using the data measured in the field with classical seismic equipment (impulse source and geophones distributed along a line). In the same place, eight transects of ERT (Wenner–Schlumberger array, 1m electrode spaced) were measured under wet and dry conditions. To calibrate the geophysical measurements, 81 boreholes (from two to 5m deep) were interpreted to determine the bedrock depth, which was defined as the occurrence in the depth of heterogeneous marine Miocene loose sandstone with centimetric laminations. ERT and SASW were found to have highly variable performances for predicting separately the bedrock depth along the hillslope. SASW correctly predicted the bedrock depth in the lower part of the hillslope, whereas the data from ERT were disrupted by shallow permanent groundwater. Conversely, ERT correctly predicted bedrock depth within the upper part of the hillslope, whereas a high variability of SASW data near the topsoil caused difficulties for bedrock depth prediction. From these results, it was possible to define an estimator of bedrock depth according to the presence of shallow groundwater, which varies along the slope, such that more importance is given to ERT estimates in the upper part of the hillslope and more importance is given to SASW in the lower part. This study shows the usefulness of such a sensor combination to estimate soil properties when the uncertainties of making predictions vary according to the geophysical methods.