Sand Formation Research Articles

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

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

Steamflood Injection Performance on 2 Types of Sand Heterogeneity in XYZ Field

Steamflood is one of the best thermal enhanced oil recovery methods to improve heavy oil production. This project focuses on the benchmarks of steamflood performance in two types of sand: homogenous and heterogeneous formations in the XYZ field. The co-kriging technique was implemented to generate the porosity and net to gross distribution. Afterward, twelve designs of experiments were run to obtain the oil production information and analyze the affecting factors of steamflood performance on each sand. The findings showed that clean sand provided higher oil production compared to the fining sand. Additionally, the well spacing had a higher contribution compared to the steam quality in applying steamflood injection. This study could serve as a guideline for engineers for planning the well spacing and steam quality utilization in steamflood injection in these two types of sand formation that contain heavy oil reserves.

Plugging Experiments on Different Packing Schemes during Hydrate Exploitation by Depressurization

Marine natural gas hydrate (NGH) can mainly be found in argillaceous fine-silt reservoirs, and is characterized by weak consolidation and low permeability. Sand production is likely to occur during the NGH production process, and fine-silt particles can easily plug the sand-control media. In view of this, experiments were conducted to assess the influence of the formation sand on the sand retention media in gravel-packed layers under gas–water mixed flow, and the plugging process was analyzed. The results show that following conclusions. (1) The quartz-sand- and ceramic-particle-packed layers show the same plugging trend, and an identical plugging law. The process can be divided into three stages: the beginning, intensified, and balanced stages of plugging. (2) The liquid discharge is a key factor influencing the plugging of gravel-packed layers during NGH exploitation by depressurization. As the discharge increases, plugging occurs in all quartz-sand packing schemes, while the ceramic-particle packing scheme still yields a high gas-flow rate. Therefore, quartz sand is not recommended as the packing medium during NGH exploitation, and the grain-size range of ceramic particles should be further optimized. (3) Due to the high mud content of NGH reservoirs, a mud cake is likely to form on the surface of the packing media, which intensifies the bridge plugging of the packed layer. These experiment results provide an important reference for the formulation and selection of sand-control schemes.

Evaluation of formation susceptibility and sand production potential in an offshore field, Niger Delta Basin, Nigeria

Wellbore instability and sand production are all common challenges in the Niger Delta oil province, resulting in high drilling and production cost as well as damage to oil facilities. The vulnerability of lithologic formations to wellbore instability and resultant sand production is investigated in the four delineated reservoirs of the “Areo” field, western part of Niger Delta Basin. The foundation for establishing the geomechanical properties in this study was a 1-dimensional mechanical earth model, using gamma ray (GR), density (RHOB), compressional slowness (DTC), and shear slowness (DTS) logs. Within the Areo oil field, two wells (well 001 and well 002) were correlated. The evaluated formations are still primarily composed of compacted shale and unconsolidated sandstone, with reservoir sand units exhibiting lower elastic and rock strength properties than shale units. High compressibility and porosity make sand more brittle, while low compressibility and porosity make shale stiffer due to high moduli. The maximum force that can be applied to a shale unit without causing it to fail is 17.23 MPa, which is the maximum average rock strength of the shale. It means that shale requires more vertical stress or pressure than sand does in order to deform it (15.06 MPa). The three sand prediction approaches used in the analysis of sand production predictions have cut-off values that are higher than the average values of the formations. The Schlumberger sand production index method (S/I) indicates that the reservoir has potential for sand influx in the two wells, with the average of the four reservoirs studied in wells 001 and 002 being 1.55 × 1012 psi and 1.14 × 1012 psi respectively. However, when a formation's sand production index is less than 1.24 × 1012 psi, as it is in this study, the formation is likely to produce sand. These findings support the notion that the defined sandstone units are highly unconsolidated and have a high potential for producing sands; therefore, sand control techniques must be factored into process optimization and cost reduction plans.

Visualization-based experimental investigation of microscopic sand production characteristics and mechanisms in weakly consolidated sandstone reservoirs

Sand production is a troublesome problem in the petroleum industry, especially in relation to weakly consolidated formations. In this work, a visual experimental apparatus, which allows sand particles to be observed, has been constructed to simulate sand production in weakly consolidated sandstone core. The experimental apparatus can accommodate sandstone core flakes as a reactor. The experiment aims to investigate the microscopic sand production mechanism of the weakly consolidated sandstone reservoir under the influence of high water cut, high clay content and polymer aging blockage. Core flakes were produced using simulated formation sands with median particle sizes of 160 μm and uniformity coefficients of 2.5, 4.6, 7.3 and 12.6, as well as clay (content 5%, 10%, 20%, 30%, respectively) and aged polymers in the wells. A total of 17 sets of experimental tests were carried out with water injection. The visual experimental results show that sand morphology presents complex wormhole. Morphology is particularly affected by core strength and heterogeneity. Based on dynamic differential pressure of experimental results, most sand production process is divided into two obvious stages, that is, the cavities formation stage of sharp sand production and the stable sand production stage. Analysis of sensitive factors revealed that the sand production rate is strongly influenced by the core strength and related to clay content, formation heterogeneity and production program. The volumetric sand production ratio decreases with the increase of core strength, with the volumetric sand production ratio (VSPR) reaching up to 0.24%. It is found that about 38% clay (1–3.91 μm) was produced in the initial stage of low flow, which is particularly evident in cores with high clay content. Moreover, for weakly consolidated reservoir, the particle competition peeling mechanism of wormhole front is proposed, and the strengthening bonding effect of aging polymer and the pore blockage effect of fine clay are clarified. The findings could contribute to better understanding of the mechanisms underlying sand production in weakly consolidated sandstone reservoirs, which also provide a solid evidence base for accurate sand production prediction and more targeted sand control.

Effect of degradation on geotechnical behavior of glauconite sands from the U.S. Mid-Atlantic Coastal Plain

Glauconite sand is a challenging sediment that can pose risks to foundation installation and performance due to its tendency to transform from coarse-grained material into fine-grained material due to particle crushing. Glauconite is characteristically green iron potassium mica and smectite often found in sand-sized peloidal form. It forms under reducing conditions within marine depositional environments below wave base and has been found in coastal plain and offshore regions of the U.S. This paper presents an overview of the geological basis for glauconite sand formation, describes its depositional environment and maturation process, and summarizes the state of knowledge of geotechnical challenges in glauconite sands. Laboratory test results are presented for glauconite sands collected from the U.S. Atlantic coastal plain, showing that initial sample conditions, drying methods, and degradation methods affect the initial, temporary, and long-term geochemical and mechanical characteristics of glauconite sands. The degree to which particles crush or degrade from their natural peloidal form to clay-size particles is linked to maturity and depositional method. Intentionally degraded specimens used in laboratory testing can simulate the effect of pile driving through creation of a shear zone of degraded soil along the pile shaft, and quantify its impact on soil-structure interface strength.

Prospects for increasing fluid production from sand and clay formations within the Precarpathian and Transcarpathian troughs

The experience of geological studies of the Precarpathian and Transcarpathian depressions indicates that the main reservoir rocks containing reservoir fluids, including gas and reservoir waters, are sand formations. There?ore, it is necessary to review the results obtained during exploration and prospecting works for gas, including within the sand-clay formations of both the Outer zone of Precarpathian and Transcarpathian depressions. In the past, many prospective gas objects were not tested in the Neogene sand-clay formations during exploration and prospecting works for gas. In the sand-clay formations, the sandiness of clays has long been considered as the ratio of the sum of all sandy layers to its total thickness. However, there are also numerous intervals between sandy layers in clay deposits, which represent thinly layered clay packages with dispersed psammitic fraction in various percentage ratios. Petrophysical parameters of these packages almost do not differ from enclosing clay rocks. As a result, many commercial gas-bearing horizons in such packages were missed. The main criterion for the gas potential of thinly layered sand-clay packages is the presence of differentiation of the psammitic fraction, which we have named sandiness. It has been established that the determination of the criterion of differentiation of the sandy fraction in the sand-clay package is best carried out by carefully studying the sludge and by applying research on the sandiness of the drilling fluid sample exiting the wellbore to the surface. When planning exploration, prosp?cting, and production of both gas and thermal water from Neogene deposits of the Outer zone of Precarpathian and Transcarpathian depressions by drilling horizontal wells, it is necessary to take into account not only the criterion of sandiness but also the sandiness of rocks. Since the thickness of such horizons is usually insignificant, inclined drilling of wells should be applied to obtain maximum fluid influxes. The application of these approaches will allow for the expansion of the hydrocarbon resource base and can also be applied to thermal water energy resources

Application of Seismic Stratigraphic Slice Continuous Browsing Technology to Delicately Characterize River Sedimentary Microfacies

On the basis of understanding the regional tectonics characteristics and stratigraphic sedimentary characteristics of the study area, the sequence stratigraphic framework within the region is gradually studied by applying the principle of high-resolution sequence stratigraphy, and G4 oil formation is divided into three sets of sand formations, namely, G4 upper, G4 middle, and G4 lower sand formations, and divided into small layers in detail. Through comprehensive analysis of lithofacies, logging facies, and seismic facies, the sedimentary facies of the G4 oil formation are comprehensively analyzed. The main sedimentary facies type of the G4 oil formation is the delta front facies belt, and the most important sedimentary microfacies in the delta front facies belt are underwater distributary channel sedimentary microfacies. Using seismic sedimentology methods, make stratigraphic slices of each sub layer of the G4 oil formation, and use the rapid browsing method of stratigraphic slices to trace river sand in detail.

Study into impacts of formation sands on foam performance during drainage gas production—Take Qinghai Oilfield’s Sebei Gasfield for example

Foam drainage gas production is a gas production technology for low-pressure gas well in domestic and abroad industries. In Qinghai Oilfield’s Sebei Gasfield, sand existence often occurs during drainage production. In order to reveal the impacts of formation sands on drainage gas production, a lab test was conducted to make a study on foam performances of different foam drainage agents in case of sand existence. A laboratory test was employed to study the foam performances of different foam drainage agents under varies scenes of sand existence, to reveal the impacts of formation sands during foam drainage gas recovery. In this study, four foam drainage agents, i.e., OP-10, Sodium dodecyl benzene sulfonate, Hexadecyl Trimethyl Ammonium Bromide (CTAB), and Lauramidopropyl Hydroxy Sulfobetaine, were selected to compare with the field compound foam drainage agent QH-X1. Following patterns can be revealed by macroscopic and microscopic experimental results: Foam formed by an ionic-type foam drainage agent is more stable when the hydrophilic sand particles are smaller (which means they have larger specific surface areas and the adsorption energy levels between the sand and bubbles are higher); while foam formed by non-ionic foam drainage agent OP-10 has a short stable period because its polarity is weaker than that of ionic-type agent foam and the adsorbability of the foam on the hydrophilic particles is weak; under different sand conditions, the impacts of different foam drainage agent types on the average bubble area, bubble wall thickness, and Plateau Boundary are markedly different, and appear decreasing tendency with anionic foam drainage agents, is the trend can be more obvious when the sand particles are coarser. The study on QH-X1 shows that the foam parameters are generally lower as the sand particles are smaller, but the changing trends can be different after sand is involved. Particles constitute an adsorption film at the gas-liquid interface and a laminar structure within each interbubble thin liquid film, thus improving bubble coalescence and unloading stability. So, the inflow of the hydrophilic sands increases the stiffness, half-life period, and comprehensive rate of the QH-X1-induced foam.

Petrophysical Study and Rock Type Determination of Siliciclastic Reservoir: Case Study Sand of Bekasap Formation, AF Field, Central Sumatra Basin, Indonesia

An integrated subsurface study has been performed for a large and mature field at the Bekasap Formation in Central Sumatra Basin. The Bekasap Formation sand represents an undeveloped reservoir because of its heterogeneity. There are five sand reservoirs (BK1, BK2, BK3, BK4, and BK5) from Bekasap Formation, which each zone or layer bounded by a flooding surface. Each sand reservoir has particular characterization based on petrophysical properties that represent geological process. The petrophysical properties consist of shale volume, porosity, and water saturation obtained by wireline log calculation. This study uses conventional core data to validate the log calculation to achieve an accurate interpretation. Bekasap reservoir is a sandstone reservoir deposited in an estuarine with tide-dominated. Formation evaluation was done to determine the interest zone by petrophysical properties. The result well-log calculation and reservoir cut-offs showed the thickest reservoir in the BK 3 with the best average values of petrophysical properties with an average shale volume 0.32; porosity of 0.245. Otherwise, in rock type determination, four lithofacies are divided in the reservoir based on flow units. The sample RT 1 and RT2 provided the best reservoir zones with HFU1 and HFU2. The RT 3 and RT 4 dominated in HFU3 and HFU4 had the lowest potential zones of reservoir. The final findings showed a good correlation between sedimentologic analysis and petrophysical properties in the rock type determination. As a result, the best reservoir quality development is controlled by the depositional environment (texture and structure) rather than the diagenetic process in this reservoir. It is proven by petrophysical properties in BK1, and BK2 is coastal barrier sand (tidal sand bar) has more clean sand rather than in BK3 and BK4 deposited in the offshore bar.

College students’ prior knowledge and alternative conceptions regarding minerals

The mineral identification lab is typically the entry level college student’s initial hands-on introduction to minerals. Our research focused on identifying alternative mineralogy conceptions that students bring to an introductory geology course and investigating the origins and nature of these conceptions. We identified a number of alternative conceptions and to help make sense of these ideas we grouped them into four categories: (1) differences between minerals and rocks (e.g., they are the same), (2) mineral composition (e.g., lighter crystals contain more air), (3) where minerals form (e.g., caves), and (4) mineral surface features. The fourth category encompassed alternative conceptions based on immediately observable features and included six daughter categories: (1) mineral characteristics (e.g., all are smooth and crystal-like), (2) origin of planar surfaces (e.g., were cut), (3) sedimentary knowledge (e.g., minerals like mica are formed from layering), (4) mineral relations (e.g., minerals of similar shape are related), (5) environmental impacts (e.g., during formation sand was incorporated to turn the mineral orange), and (6) age of minerals (e.g., age can be determined by fragility). Further, we identified three main knowledge sources from which students construct alternative conceptions: (1) prior science courses, (2) outdoor activities, and (3) jewelry and solar and water impacts. Our research adds to previous work on the alternative conceptions held by novice earth science students. Students’ answers reflect how their knowledge can contribute to creating alternative conceptions.

Approaches to the Treatment of Patients with Upper Urinary Tract Stones and Comorbid Vascular and Cardiological Pathology

Urinary stone disease (USD) is associated with the formation of sand and calculi in the organs of the urinary system. This is a common chronic pathology, which is characterized by the frequent exacerbations and a severe course. Without timely treatment, USD threatens of the urinary tract blockage and intoxication of the organism. The article emphasizes the importance of carefully the treatment choose of patients with stones of the upper urinary tract and vascular and cardiac pathologies, because these nosologies have common etiological links and are related to age and sex. An analysis of methodological and scientific literature was carried out to study approaches to the treatment of patients with USD with comorbid vascular and cardiac pathologies. Various methods were used, namely: the search for methodological and scientific literature, in particular induction and deduction, comparison, classification, systematization, abstraction and specification, analysis of documentation. The analysis of approaches to the treatment of patients with stones of the upper urinary tract demonstrated that there are two main approaches to treatment – conservative therapy and surgical treatment. Due to a number of reasons, conservative medical treatment can be used only in some cases as the method of choice for the treatment of patients with USD. The use of extracorporeal shock wave lithotripsy (ESWL) for the destruction of stones in the kidneys and ureters significantly increases the effectiveness of treatment of the patients. However, in patients who were operated for cardiovascular pathology, in the case of complete withdrawal of anticoagulant therapy, even for a short period, the risk of complications increases. Therefore, before performing ESWL in such patients, it is recommended to reduce the anticoagulant dose or switch to low-molecular-weight heparins 3-4 days before the planned surgical intervention. During the treatment of patients with calculi of the upper urinary tract and vascular and cardiac pathologies, a careful choice of treatment and the involvement of related specialists are necessary.

Collapse failure analysis of S13Cr-110 tubing in a high-pressure and high-temperature gas well

Due to excellent CO2 corrosion resistance and low cost, martensitic stainless steels such as super 13Cr have been widely used as tubing strings in high-pressure and high-temperature wells. However, in recent years, with the further development of the oilfield, super 13Cr tubing failure accidents keep happening in high-pressure and high-temperature gas well, resulting in the loss of well integrity and huge economic losses. So a systematic research on the failure mechanism of the super 13Cr tubing in HPHT gas well under different service conditions is vital to the reduction of the failure accidents. In this paper, a collapse failure accident of S13Cr-110 tubing in a high-pressure and high-temperature gas well was investigated by metallographic microscope, scanning electron microscope, energy dispersive spectrometer, X-ray diffraction and finite element analysis, aiming to find out the root causes and put forward useful suggestion for the establishment of the preventive measures. The results showed that the chemical composition and mechanical properties of the tubing were all in accordance with the corresponding parameter requirements, and the collapse failure was attributed to the combined effect of formation sand production, high temperature and stress corrosion cracking on the outer surface. The tubing plugging induced by the formation sand production caused the increase of pressure difference between the annulus and tubing, which was the main reason for the collapse failure. In addition, high temperature in the downhole would result in a decreasing of the tubing’s anti-collapse ability. Meanwhile, the annular environment containing Cl-, PO43-, further induced the stress corrosion cracking under service stress. The presence of the cracks on the outer surface could cause a significant decrease of the pressure-bearing capacity of tubing strings, which would finally have an obvious influence on the acceleration of the failure process.

Porous media flooding mechanism of nanoparticle-enhanced emulsification system

This study carried out interfacial tension (IFT) testing, sand surface element analysis and scanning electron microscope imaging, rock–oil–emulsification system interaction testing, and microstructure, droplet size distribution, and stability of oil in water (O/W) emulsion to clarify the porous media flooding mechanism of a hydrophilic nano-SiO2 enhanced emulsification system. The results show that by adding a small amount of nano-SiO2 (0.01 wt. %) into an anionic surfactant fatty alcohol polyoxyethylene ether sodium hydroxypropyl sulfonate (AEOSHS) solution (0.5 wt. %), the IFT of oil–water was effectively reduced, the adsorption loss of AEOSHS on the formation sand surface was reduced by more than 70%, and the droplet size of the formed O/W emulsion was reduced by 50%. This greatly improves the effective concentration of AEOSHS and emulsifies the heavy oil ability in the formation away from the injection well. Moreover, the spreading ability of oil on the core surface is greatly reduced, and the width of the diffusion zone is narrowed. Meanwhile, a very clear dividing line of oil can be seen, which shows that the wettability of the core has changed to water wet. The stability of the formed O/W emulsion was further enhanced, and the coalescence and migration process of the droplet is extremely slow. The oil recovery of the AEOSHS + nano-SiO2 system can effectively increase 21.95% of the original oil in place. Both the sand-packed tube experiment and the microscopic visual oil flooding experiment show that the system can not only expand the swept volume but also improve the oil displacement efficiency, which means that the combined system can significantly improve the oil displacement effect.

A terminal Messinian flooding of the Mediterranean evidenced by contouritic deposits on Sicily

ABSTRACTThe evolution of marine gateways and sea straits exerts major control on bottom current depositional systems. A well‐known interval in geological history characterized by frequent changes in marine connectivity is the Messinian Salinity Crisis (5.97 to 5.33 Ma) when the Mediterranean allegedly experienced major (>1 km) sea‐level drawdown followed by a catastrophic marine replenishment at the base of the Zanclean. Controversy exists around the timing and mode of this event as unambiguous flood deposits have so far never been drilled or recognized in outcrops. In the Sicilian Caltanissetta Basin (Italy), the Messinian/Zanclean boundary is directly underlain by the Arenazzolo Formation. This 5 to 7 m thick sandy sedimentary interval may reveal a genetic link with the abrupt refilling of the Mediterranean, but at present a detailed study to understand its origin is lacking. In this work, the Arenazzolo Formation at Eraclea Minoa has been studied by a multi‐method approach, employing detailed facies description, grain‐size analyses, petrographic analyses and palaeocurrent analyses. Palaeogeographical reconstructions and facies associations show that the Arenazzolo Formation sands were deposited on the northern flank of the Gela thrust front by persistent bottom currents, flowing parallel to the regional slope physiography, during a transgression. It is hypothesized that these currents are associated with the active circulation of surface and intermediate water masses coeval with a terminal Messinian flood, when basin margins overtopped and a reconnection between western and eastern Mediterranean was created. The Arenazzolo Formation is a unique example of a contouritic deposit formed by bottom currents that establish during the reconnection of major isolated water bodies.

PRE- FOUNDATION STUDIES USING VERTICAL ELECTRICAL SOUNDING AND SOIL SAMPLE ANALYSIS

Subsurface rock properties investigation to categories foundation competent layer for the proposed engineered structure capable of housing offices, lecture halls, and laboratories was carried out using geophysical (GPHY) and geotechnical (GTECH) techniques. Electrical resistivity GPHY technique using vertical electrical sounding (VES) field procedure was utilized in which nineteen (19) VES spots were occupied. Results of the VES revealed 2-D subsurface geoelectric sequences comprising of incompetent overburden layer of about 5 m thick with resistivity value between 10 and 210 ohm-m typical of clay soil material. Beneath this layer are sand formation and fresh bedrock with resistivity range of 750 to 1000 ohmm, which are good formations for foundation. Additionally, according to GPHY studies, western and northern portions of the region are marked by fractures/faults, which could cause building subsidence if foundation is stationed at these points. The results of the analyses of the soil samples taken in five different points in the study area revealed: (1) grain size distribution with 0.075 mm particle size passing of an average of 41% signifying the occurrence of clay, corroborating the presence of clay material within the weathered layer in GPHY investigations; (2) active and expansive nature of the soil with linear shrinkage greater than 8% revealing unsuitability of topsoil for foundation; (3) medium plasticity of soil indicating possible soil swelling; and (4) concomitant GTECH and GPHY results of the topsoil and weathered layer properties. The overburden layer with clayey materials must be removed and areas with geological structures must be taken into account.

Experimental study on penetration characteristics of an open-ended pile under static and dynamic driving methods

Open-ended piles have been widely adopted in both offshore and onshore geotechnical engineering projects. However, the influence mechanism of pile driving methods on the penetration characteristics of the open-ended piles is not clear. Therefore, this paper presents simulations of an open-ended pile penetrating through a silt layer to a fine sand bearing stratum using static and dynamic driving methods respectively in a series of indoor model tests. Properties including pile sinking resistance, pile end resistance, pile side friction resistance, pile load transfer law and soil plug formation during penetration are analyzed. The results show that the PLR value of the hammered pile is always greater than that of the static pressure pile in the stable sinking stage, while the IFR value of the latter in the sand layer is significantly higher than that of the former. The resistance of the hammered pile under the same penetration depth is less than that of the static pressure pile and increases sharply when entering the holding layer. In addition, the final pile driving resistance of the hammering method is 66.68% of the static pressure pile driving resistance, and the pile end resistance from the static pressure method and hammering method account for 75.4% and 77.6% of the total resistance respectively In the choice of construction method, the static pressure method is more suitable for silty soil, and the hammering method can show its advantages in fine sand formation.

Evaluation of the consolidation status of heavy oil sands through rock physics analysis: A case study from Fengcheng oilfield

Heavy oil is an important unconventional oil resource with huge availability worldwide, which also forms the primary oil source in Fengcheng oilfield, XinJiang, China. The elastic properties and consolidation status of heavy oil sands are of significant values as they can provide guidance for reservoir exploration and production. However, due to the lack of detailed rock physics investigation of the heavy oil sands in Fengcheng oilfield, the knowledge about their micro-scale elastic properties and consolidation status is still limited. Based on the well log data and laboratory measurements, we performed rock physics analysis of the heavy oil sands’ elastic properties. We first analyzed the well logs to determine the oil sands formations and then quantitatively delineated the relations between density, porosity, and velocity. Combining with laboratory measured data, we applied theoretical rock physics models to characterize the consolidation status of the heavy oil sands. Our results show that the oil sands in this area are poorly consolidated with a loose rock frame. Overall, this study highlights the micro-scale elastic properties of the heavy oil sands in Fengcheng oilfield and also reveals the consolidation status. It presents a method of integrating well log, laboratory data, and rock physics analysis to evaluate the consolidation status of heavy oil sands, which can facilitate the future detailed petrophysical analysis and provide important information for seismic characterization and drilling risk evaluation.

Some geomorphological implications of recent archaeological investigations on river terraces of the River Dee, Aberdeenshire

Excavation and survey of archaeological sites have in recent years generated new data on the chronology of river terraces on the River Dee between Banchory and Peterculter in Aberdeenshire. Terrace fragments have been mapped and correlated on altitudinal grounds, for the first time. Five terrace surfaces are identified and named, refining the terminology of the British Geological Survey. Three are distinct surfaces within the Lochton Sand and Gravel Formation. The relation between them, regional deglaciation and the formation of the Late Devensian Loch of Park, north of Crathes, suggests some time separated their development. Below these, a fourth terrace, the Camphill Terrace, is dated to before the Windermere Interstadial by finds of Late Upper Palaeolithic flints. The Camphill Terrace is argued to have been the active valley floor within the Younger Dryas also. Timing of incision from the Camphill Terrace is not understood: interpretations are different at three archaeological sites. The youngest terrace fill and surface, the Maryculter Terrace, began to form c . 5000 years ago.

Gravel padding filters for combating sandblasting in wells

This paper presents an analysis the technology for creating an artificial gravel pack behind the casing in the near-wellbore part of the formation in producing oil and gas wells. Gravel-embedding filter is not only a special device installed in the well to clean the fluid extracted from the formation of sand and other foreign impurities, but also the use of gravel in conjunction with the filter in order to retain the formation sand at the site of its occurrence. Wells are equipped with gravel filters when completing them in formations represented by medium to fine grained and silty sands. The desiccant layouts of gravel stuffing filters on lightly cemented sandstones are presented in the work show high efficiency, as they prevent the removal of sand during the well operation. Creating an artificial gravel pack is an effective way to prevent sand from entering the well.