Sand Migration Research Articles

Measurement of Sediment Concentration of the Oscillatory Flow in the Surf- and Swash-zone

Wang, J.; Qu, Z.; Xu, Z.; Shim, J.S.; Liang, B., and Lee, D.Y., 2018. Measurement of Sediment Concentration of the Oscillatory Flow in the Surf- and Swash-zone.. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1231–1235. Coconut Creek (Florida), ISSN 0749-0208.The sediment transports near the bed need to be accurately observed to validate the existing models that are based on the empirical formula for the sediment flux and to develop more realistic morphology prediction model. One of the essential tasks for the evaluating the existing models and developing new one is the precise measurement of the sediment transport at swash zone without disturbing flow. Different methods in estimating the sediment transport rates at the surf-zone and swash-zone such as measuring the time evolution of the bed profile, sand ripple volume and migration speed are investigated and evaluated. To develop more reliable estimation of the sediment flux by measuring the vertical profiles of sediment concentration and velocity without disturbing the flow conditions, method of estimation of the vertical sediment concentration profile by detecting the backscattered light intensity using high quality camera was tested and evaluated. The problems of different methods in estimating the sediment flux are identified and discussed.

Organosilane film for sand migration control based on in-situ hydrolysis and polycondensation effects

Loosely consolidated or unconsolidated reservoir is susceptible to sand migration that results in rapid production decline and short-lived stimulation enhancement. In this study, water-soluble organosilane used for sand migration control was proposed by considering in-situ hydrolysis and polycondensation effects. A variety of organosilanes were screened by evaluating their hydrolysis and polycondensation rate. The suitable structure of organosilane for sand consolidation was determined. Based on the selected organosilane FX, various factors influencing hydrolysis and condensation rates were studied to determine the usage of organosilane. The result indicates that the rate of hydrolysis and polycondensation dominates the consolidation performance of organosilane by changing the amount of active Si-OH reacting with sand surface. HCl was used to control hydrolysis and polycondensation rate of the organosilane with appropriate formation temperature, operation and shut-in time. The various process control parameters were optimized with the organosilane concentration of 3%–5%, the catalytic HCl concentration of 1%–3%, and formation temperature lower than 100 °C. Static and dynamic sand stabilization experiment showed that the organosilane had a high compressive strength, little loss of permeability, long-term stability against typical formation fluids, and wide compatibilities with various types of acidizing slug. Micro-experiment confirmed the in-situ generation of a hydrophobic film on the touchpoint of sand surface connecting migrated sand with matrix.

Flow onset of fresh mortars in rheometers: Contribution of paste deflocculation and sand particle migration

Shear-induced particle migration is widely recognized to be a challenge in characterizing the rheological properties of fresh cement-based mortars. In this study, we aim to quantify shear-induced particle migration by characterizing the stress decay process during constant shear flow with the aid of a modified thixotropy/migration model. It is found that a conventionally used single exponential model is not sufficient to fit the stress decay and describe the destructuration and sand migration of mortar under shear. Instead, a two exponential model is needed to capture the interaction of sand particles and the suspending cement paste phase. Model parameters are used to quantify the effect of sand volume fraction, clay addition, and applied shear rate on the kinetics and intensity of colloidal deflocculation and sand migration. Results provide evidence that the colloidal and granular contributions to the overall stress decay of mortars can be represented by each of the two exponentials.

Nanoparticle induced chemical system for consolidating loosely bound sand formations in oil fields

Migration of sand loosely bound, and younger age formation causes severe problems in the hydrocarbon production. Several techniques and methods have been implemented in field to control the sand production but only a few have been successful partially to stop sand migration to wellbore and subsequently to the surface. Rendering the formation sand particles immobile by binding them together at their contact point is the best option in controlling the migration of it.The present study proposed a new consolidating agent for controlling the sand grains migration as well as in-situ consolidation. The ability of this nanoparticle induced chemical solution to bind the sand grains together at their contact point in the absence and presence of hydrocarbon was evaluated. It is observed that addition of nano-SiO2 in the urea formaldehyde can enhance its mechanical properties as well as water resistance. A great compressive strength (>2000psi) was gained with a little reduction in the permeability. To evaluate the interaction between the nano-SiO2-Urea-Formaldehyde (UF) solution and silica sand, the FT-IR and TGA were performed. Influence of clay present with sand on the consolidation was also evaluated. The effects of pressure drawdown and flow rate on consolidation was examined to evaluate the critical flowrate at which the sand particle starts dislodging from the consolidated mass which in turn signifies the durability of the consolidation. The field application of this technique will optimize hydrocarbon production and flow assurance.

Reflection of the Baltic Sea Lithuanian nearshore bottom peculiarities in the historical maps

Using the bathymetry information available from historical maps, the underwater slope of the Baltic Sea in the Lithuanian area of the shore is analysed south and north of the Klaipėda harbour. For this purpose, the old depth measurements have been converted into the metric system and cross profiles of the nearshore drawn, as well as, on this basis, the diagrams for the 3, 5, 7 and 10 m depth points have been constructed. The depth data from the maps compiled in 1743, 1855, 1875 and 1913 have been analysed. These periods correspond to specific conditions of the shore zone morpho- and litho-dynamics. In 1743 there was no beach protecting the dune ridge on the Curonian Spit, and sand was driven by wind from the shore zone to the large dunes. There were no hydro-engineering structures in the Klaipėda harbour; therefore nothing impeded sand migration along the shore. In 1855 the shores of the Klaipėda channel were fixed, but there were no harbour piers yet. In 1875, the piers were freshly built and a beachprotecting dune ridge partly formed. In 1913, this dune ridge was already finished and the Klaipėda port was fully functioning with 5–6 m depths at the port gates. Conclusions are made about the former bottom relief during different stages of the nearshore evolution and about the conditions which caused its changes.

The provenance of Taklamakan desert sand

Sand migration in the vast Taklamakan desert within the Tarim Basin (Xinjiang Uyghur Autonomous region, PR China) is governed by two competing transport agents: wind and water, which work in diametrically opposed directions. Net aeolian transport is from northeast to south, while fluvial transport occurs from the south to the north and then west to east at the northern rim, due to a gradual northward slope of the underlying topography. We here present the first comprehensive provenance study of Taklamakan desert sand with the aim to characterise the interplay of these two transport mechanisms and their roles in the formation of the sand sea, and to consider the potential of the Tarim Basin as a contributing source to the Chinese Loess Plateau (CLP). Our dataset comprises 39 aeolian and fluvial samples, which were characterised by detrital-zircon U–Pb geochronology, heavy-mineral, and bulk-petrography analyses. Although the inter-sample differences of all three datasets are subtle, a multivariate statistical analysis using multidimensional scaling (MDS) clearly shows that Tarim desert sand is most similar in composition to rivers draining the Kunlun Shan (south) and the Pamirs (west), and is distinctly different from sediment sources in the Tian Shan (north). A small set of samples from the Junggar Basin (north of the Tian Shan) yields different detrital compositions and age spectra than anywhere in the Tarim Basin, indicating that aeolian sediment exchange between the two basins is minimal. Although river transport dominates delivery of sand into the Tarim Basin, wind remobilises and reworks the sediment in the central sand sea. Characteristic signatures of main rivers can be traced from entrance into the basin to the terminus of the Tarim River, and those crossing the desert from the south to north can seasonally bypass sediment through the sand sea. Smaller ephemeral rivers from the Kunlun Shan end in the desert and discharge their sediment there. Both river run-off and wind intensity are strongly seasonal, their respective transport strength and opposing directions maintain the Taklamakan in its position and topography.

Analysis of Desert Sand Dune Migration Patterns from Landsat Image Time Series for The Southern California Desert

Developers of renewable energy installations in southern California need to evaluate the risks to facility operations from proximity to active desert dunes. This study first validated Landsat image spectral data using ground-based data collection of aeolian sand migration rate measurements surveyed in Arizona as an accurate method for characterizing dune mobility. The predominant direction of measured sand dune movements was correctly mapped at this site from the satellite imagery, as well as the migration distances of the leading edges of sand dunes over the entire 1992-2010 monitoring period. Application of the Landsat image method to two dune systems in southern California demonstrated its usefulness for mapping sand migration patterns and rates. Between 1995 and 2014, Palen Dunes lost over half of its stable dune surface and increased its sand accumulation zone by nearly that same area coverage. In contrast, changes in the sand movement patterns at Kelso Dunes were not apparent, perhaps due in to its more constraining mountain landscape features. These results have an immediate application for understanding future sand transport and characterizing potential impacts to nearby utility-scale solar energy installations.

‘This restless enemy of all fertility’: exploring paradigms of coastal dune management in Western Europe over the last 700 years

Drifting sand has inundated settlements and damaged agricultural land along the coasts of Western Europe for the last 700 years. The need to control sand migration has been an important driver of the management of coastal sand dunes and here we analyse original archival materials to provide new insights into historically changing coastal dune management practices. Records of coastal sand movement in Denmark, The Netherlands, Britain, Ireland and France were reviewed and three distinct management approaches were identified. The ways in which these approaches have played out in space and time were examined with particular reference to records from landed estates in Britain and Ireland. We demonstrate how historical evidence can be used to inform contemporary debates on dune management strategy and practice. We propose a new place‐based approach to the future management of coastal dunes that can incorporate both expert and locally produced ‘knowledges’ and that is underpinned by an understanding of how both natural forces and human interventions have shaped these dune landscapes over time.

CWENOスキームによる浸透破壊中の砂の移動と浸透流の数値シミュレーション

浸透破壊に至るまでの砂（の塊）は固体として扱うことができるが，浸透破壊後は有効応力を失うことで流体のようにふるまう。本論文では，固体から流体へと変化する浸透破壊前後の砂の挙動を連続的にシミュレートするための数値解析手法を提案する。流動化した砂の挙動を解析するため，砂と浸透水の両方についてオイラー表記された連続式と運動方程式を支配方程式とする。双曲型の偏微分方程式となる支配方程式を，安定的かつ高精度に解くためCWENO（Central Weighted Essentially Non-Oscillated method）スキームを採用する。ここでは，1次元及び2次元のダルシー流の計算精度を確かめた後，上向き浸透流による砂のボイリングについての数値計算に取り組む。提案手法は浸透破壊前後の浸透流及び砂の挙動を連続的に計算することを可能にし，計算された浸透破壊後のそれらの速度は理論解と良好に一致することが示される。

Geological evidence for a drought episode in the western Pampas (Argentina, South America) during the early–mid 20th century

Drought episodes during the early–mid 20th century were recognized and described in several places around the world, with extreme dry conditions and widespread landscape denudation, like during the famous ‘Dust Bowl’ in North America. However, there is scant documentation of droughts in southern South America, particularly from the Pampas, and none based on the geological record. In this article, we provide clear evidence of aeolian reactivation and sand deposition in some areas of La Pampa and San Luis provinces, western Pampas (Argentina), during early–mid 20th century in response to drier conditions, probably amplified, like historic droughts in North America, by anthropogenic factors (e.g. significant population increase and agriculture expansion into a fragile environment). Evidence includes widespread bare sand blowouts, extensive surfaces with active sand migration, steep dune lee slopes, and sharp crests covered by weak soil development (A/C profile), accompanied by historical documents. Optically stimulated luminescence (OSL) ages on aeolian beds confirm mobilization and sedimentation by wind processes c. 95–60 yr BP. Considering the dominant (over 70%) austral spring–summer precipitation, it is possible the rainfall deficit in western Pampas was linked to positive sea surface temperature (SST) anomalies in the western subtropical South Atlantic Ocean (20–30°S and 30–50° W), according to significant canonical correlation between the precipitation field in subtropical South America and the Atlantic Ocean SST anomalies.

Mechanism analysis and process optimization of sand and plug removal with rotating jet in horizontal well

In the view of the problems existing in horizontal well, such as sand depositing and cleaning difficulty of borehole, a technology with rotating jet suitable to resolution of the problems was presented. Based on liquid-solid two-phase flow theory, the analyses on the sand movement law and the swirling field influential factors were conducted. Results show that: 1) With the increasing of displacement in horizontal section annulus, swirling field strength increases, and when the displacement is constant, the closer from the nozzle, the stronger the swirling field strength is; 2) Head rotating speed and liquid viscosity have little influence on the swirling field strength, but the sand-carrying rate of fluid can increase by increasing liquid viscosity in a certain range; 3) Rotating the string and reducing its eccentricity in annulus are conducive for sand migration in the annulus; 4) The sand can be suspended and accelerated again and the swirling field strength is enhanced by the helix agitator. Hence, the research results provide the theoretical basis for the design and application of rotating jet tool.

The last mangroves of Marajó Island — Eastern Amazon: Impact of climate and/or relative sea-level changes

The dynamics, over the last 7500years, of a mangrove at Marajó Island in northern Brazil were studied by pollen and sedimentary facies analyses using sediment cores. This island, located at the mouth of the Amazon River, is influenced by riverine inflow combined with tidal fluctuations of the equatorial Atlantic Ocean. Herbaceous vegetation intermingled with rainforest dominates the central area of the island, while várzea is the main vegetation type along the littoral. In particular, the modern northeastern coastal zone is covered by a mosaic of dense rainforest, herbaceous vegetation, mangroves, várzea, and restinga. The integration of pollen data and facies descriptions indicates a tidal mud flat colonized by mangroves in the interior of Marajó Island between ~7500calyr BP and ~3200calyr BP. During the late Holocene, mangroves retracted to a small area (100–700m in width) along the northeastern coastal plain. Mangrove expansion during the early and mid Holocene was likely caused by the post-glacial sea-level rise which, combined with tectonic subsidence, led to a rise in tidal water salinity. Salinity must have further increased due to low river discharge resulting from increased aridity during the early and mid Holocene. The shrinking of the area covered by mangrove vegetation during the late Holocene was likely caused by the increase in river discharge during the late Holocene, which has maintained relatively low tidal water salinity in Marajó Island. Tidal water salinity is relatively higher in the northeastern part of the island than in others, due to the southeast–northwest trending current along the littoral. The mixing of marine and riverine freshwater inflows has provided a refuge for mangroves in this area. The increase in flow energy during the last century is related to landward sand migration, which explains the current retraction of mangroves. These changes may indicate an increased exposure to tidal influence driven by the relative sea-level rise, either associated with global fluctuations or tectonic subsidence, and/or by an increase in river water discharge.

Response of perforated composite tubes subjected to axial compressive loading

Perforated and slotted tubes are widely used as liners in oil and gas industry to facilitate the collection of products from reservoirs, and prevent sand migration to wellbore, which in return could cause product contamination and affect functionality of the pumps. The objective of this research is to establish the critical axial load of perforated E-glass/epoxy tubes using numerical and experimental methods. Firstly, in an experimental attempt, a total of six sets of composite tubes (three sets with perforations and three sets of intact (non perforated) tubes), having two different thicknesses and diameters, were fabricated and tested under axial compression. The reduction in the critical load and axial stiffness of the composite tubes was investigated experimentally. Secondly, a comprehensive numerical investigation was carried out, using the finite element method (FEM), to simulate the instability response of the intact and perforated composite tubes under compressive axial loading. The effect of various parameters such as the tube diameter, size, number of perforation and wall thickness were investigated in the current research. Good correlation is obtained between the experimental and numerical results. According to the results, the intact and perforated tubes showed similar instability mode shapes under the axial loading. However, the critical load and global stiffness of the perforated tubes were considerably reduced.

Influence of environmental factors on the abundance of Anopheles farauti larvae in large brackish water streams in Northern Guadalcanal, Solomon Islands

BackgroundThe main vector of malaria in Solomon Islands is Anopheles farauti, which has a mainly coastal distribution. In Northern Guadalcanal, Solomon Islands, high densities of An. farauti are supported by large brackish streams, which in the dry season are dammed by localized sand migration. The factors controlling the high larval productivity of these breeding sites have not been identified. Accordingly the influence of environmental factors on the presence and density of An. farauti larvae was assessed in three large naturally dammed streams.MethodsLarval sites were mapped and anopheline larvae were collected monthly for 12 months (July 2007 to June 2008) from three streams using standard dippers. Larval collections were made from 10 locations spaced at 50 m intervals along the edge of each stream starting from the coast. At each collection point, floating filamentous algae, aquatic emergent plants, sun exposure, and salinity were measured. These environmental parameters along with rainfall were correlated with larval presence and density.ResultsThe presence and abundance of An. farauti larvae varied between streams and was influenced by the month of collection, and distance from the ocean (p < 0.001). Larvae were more frequently present and more abundant within 50 m of the ocean during the dry season when the streams were dammed. The presence and density of larvae were positively associated with aquatic emergent plants (presence: p = 0.049; density: p = 0.001). Although filamentous algae did not influence the presence of larvae, this factor did significantly influence the density of larvae (p < 0.001). Rainfall for the month prior to sampling was negatively associated with both larval presence and abundance (p < 0.001), as high rainfall flushed larvae from the streams. Salinity significantly influenced both the presence (p = 0.002) and density (p = 0.014) of larvae, with larvae being most present and abundant in brackish water at < 10‰ seawater.ConclusionThis study has demonstrated that the presence and abundance An. farauti larvae are influenced by environmental factors within the large streams. Understanding these parameters will allow for targeted cost effective implementation of source reduction and larviciding to support the frontline malaria control measures i.e. indoor residual spraying (IRS) and distribution of long-lasting insecticidal nets (LLINs).

Mississippi Valley regional source of loess on the southern Green Bay Lobe land surface, Wisconsin

Loess has been recognized on the glacial land surface of the Green Bay Lobe for over 100 yr, but no systematic explanation of the source of the loess has been advanced. Intriguingly, the loess on the Green Bay Lobe land surface is thicker than predicted by regional thinning trends from the Mississippi Valley and is geographically separated from much loess of southwest Wisconsin by a sandy region devoid of loess. Mapping based on soil survey interpretation indicates that the loess occurs above an escarpment marking the eastern end of the sandy loess-free region. Particle size fining trends demonstrate that the loess was transported by northwesterly winds. Clay mineralogy of the Green Bay Lobe loess is distinctly different than glaciogenic sediments and matches loess of the Mississippi Valley, indicating a regional source and long distance transport of the loess. We propose the loess was transported from the regional source along a surface of transport produced by migration of eolian sand through low-relief landscapes including the glacial Lake Wisconsin basin. Eolian sand migration caused repeated entrainment of dust leading to east-southeastward transport. The loess accumulated above an escarpment that limited sand mobility and re-entrainment of loess beyond this topographic barrier.

Multiple‐Year Water Balance of Soil Covers in a Semiarid Setting

Surface covers are used to isolate contaminants in hazardous and low-level radioactive sites for time frames ranging from hundreds of years to millennia or more. In the absence of data for such durations, the long-term performance of surface barriers can only be represented with short-term tests or inferred from analogs and modeling. This paper provides evidence of field performance of soil covers for periods up to 17 yr. The results of lysimeter studies from a semiarid site in Washington State show that a cover design known as the Hanford Barrier, which consists of 1.5 m of silt loam above a sand-gravel capillary break, can nearly eliminate drainage. The results were similar if plants were present or not, demonstrating the robustness of the design. Furthermore, reducing the silt loam thickness to 1.0 m (as might occur via erosion), with or without plants, did not lead to drainage. When irrigated to mimic 3x average precipitation conditions, the vegetated Hanford Barrier continued to prevent drainage. Overall, the results showed no loss in performance during the 17 yr of testing. Only when plants were eliminated completely from the 3x precipitation test did drainage occur (rates ranged from 6 to 16 mm yr(-1)). In a separate test, replacing the top 0.2 m of silt loam with dune sand and reducing the plant cover did not lead immediately to the onset of drainage, but soil matric heads within the silt loam noticeably increased. This observation suggests that dune sand migration onto a surface cover has the potential to reduce a cover's ability to minimize deep drainage.

Pleistocene and Holocene pattern of sand migration along the Mediterranean littoral of Israel

Pleistocene and Holocene pattern of sand migration along the Mediterranean littoral of Israel

A Critical Review Of Existing Gravel-Pack Design Criteria

Abstract There are numerous design criteria available for gravel-packs based on the well-mown gravel-la-sand grain size ratio. These rules are mainly derived from the interpretation of compatibility experiments. The favourable gravel-to-sand ratios are determined within the limits set by successful and unsuccessful tests. Because of empirical approach, various influences have to be considered due to different test setup and evaluation of experiments. In this paper, the types of design criteria, the similarities and differences between the various methods, the uncertainties in the use of these design criteria, and the gaps in current knowledge are described. Applicability of these purely geometrical methods under fluctuating flow, methods relating to sand retention, permeability impairment, clogging and acceptable quantity of sand within a certain depth of penetration into the gravel are discussed. Introduction Since gravel-packs are recognized as the most popular sand prevention method. numerous gravel-pack design criteria have been developed roughly a quarter of a century ago. These methods have ranged from using simple geometrical approach on easily measurable sand and gravel properties to performing filtration tests with representative reservoir sand and the proposed gravelpack. The latter have generally been regarded as being better indicators of future gravel-pack performance. However, as sand pratic1es of reservoirs are structured at random, it is almost impossible to describe interaction between sand and gravel theoretically in a rigorous manner. All existing gravel-pack design criteria are more or less based on laboratory tests with defined sand-gravel combinations and can therefore only be applied in connection with the respective combinations and test conditions. However, despite careful application of these rules, high pressure drop and reduction in production rate are still associated with this exclusion technique. Consequently, a gravel-pack seems to change its structure. permeability and pressure differential over the course of a filtration period. Thus, there is a certain unpredictability about the process of sand exclusion due to the inability of fully describing the mechanisms and the properties of gravel-sand/fluids system and of relating properties and mechanisms to the performance of aterials. So far, there is not much known about the reliability of gravel-packs that are designed on the basis of different geometrical criteria, in particular in cases where the grain size distribution of the produced formations is not well known. In addition, performance tests only qualitatively evaluate gravel-packs, and therefore discourage improvement of gravel-pack design by not providing quantitative performance measures. Gravel-pack design methods based on gravel-to-sand size ratio results have been more readily accepted because they are easy to use and easily implemented into practice. However, there is considerable variability between these methods, and such methods do not adequately address sand migration, clogging and permeability impairment. In addition, these conventional design criteria rely completely on the geometrical condition that the pores of the gravel have to be smaller than the sand panicles to prevent sand from being transported through the pores of the gravel-pack.

Post Core Analysis to Determine the Steam Flow Path In the McMurray Oil Sands

Abstract Core analysis was performed on core material extracted from three post-recovery core holes drilled at distances varying from 12 to 20 m from a wellbore that had experienced eight cycles of steam injection/production (I/P). The objective was to evaluate the success of cyclically steaming the McMurray oil sand by ascertaining steam placement and the effect of steam on the reservoir mineralogy. Post core-hole analysis was compared to the original core of the centrally located I/P well using standard techniques plus a number of special core analyses. X-radiography, connate water analysis, tracer analysis, absolute and effective permeability measurements, petrographic analysis, in addition to selected open-hole and cased-hole logs were included in these special studies. Results showed that reduction in oil saturation over the oil sand interval was attributed to steaming and/or a combination of condensed steam invasion and drilling mud invasion. The actual steam-invaded zone was shown to be a lesser portion of the total oil sand pay which could be correlated with the special core analyses and with temperature logs. This paper describes the procedures used to assist in determining steam zones and includes an interpretation of the data as well as a critique of the analyses. Introduction In-situ bitumen recovery from the Athabasca oil sands, the largest oil sand reserves in the world, has not yet been commercialized. Successful steam recovery processes such as cyclic steam at Cold Lake(1) or steam drive at Peace River(2), have had limited success when applied in the McMurray oil sands formation at PCEJ(3,4) and GLISP(5). A number of factors have been recognized which make in-situ recovery from this resource more difficult:Lower reservoir temperature and pressure, higher bitumen viscosity, and sand migration prevent primary production. Typical reservoir properties in the PCEJ Hangingstone lease are presented in Table 1.Shallow depth of burial and low initial breakdown pressures(6) combined with very high bitumen saturation, limits leak-off of the injected steam and encourages fracturing. Less placement of heat near the wellbore results in lower calendar day oil rates (CDOR).A combination of vertical and horizontal fractures(3,7,8) ("T" Fractures) tend to make bitumen recovery schemes more complicated and less productive. A ("T" fracture is shown in Figure 1 as an initial vertical fracture climbing at 45 degrees from the perforations up into the shaley oil sand above, where it turns horizontal and can even travel back to the well, but at a shallower depth. Horizontal fractures in the upper shaley oil sand do not characteristically produce much bitumen even though it may hold up to 40% of the total injected steam. TABLE 1: Typical properties of McMurray oil sand (Hangingstone). (Available in full paper) Steam injection fractures were utilized to heat the formation at the PCEJ Hangstone Pilot Project located 45 km south-west of Fort McMurray. Different steam placement strategies were rested in individual cycles and in various isolated wells in an attempt to keep the heat within the rich oil sand. This was done by controlling injection rates, quality and volume injected.

Offshore Hydraulic Fracturing Technique

Technology Today Series Summary This paper describes the "frac-and-pack" completion technique currently being used in the Gulf of Mexico, and elsewhere, for stimulation and sand control. The paper describes process applications and concerns that arise during implementation of the technique and discusses the completion procedure, treatment design, and execution. Introduction An innovative well-completion technique, frac and pack, recently has been introduced into Gulf of Mexico well-completion operations. The technique combines the stimulation advantages of hydraulic fracturing with the sand-control technique of gravel packing. The method involves a one-step fracturing and gravel-packing operation performed through conventional downhole gravel-packing hardware. The technique is being used successfully to reduce skin damage effects and to improve the productivity of unconsolidated sandstone completions significantly by creating better communication between the wellbore and the reservoir. An example of the productivity improvement related to frac and pack is provided in the Conclusions and References. Successful fracturing of soft formations poses challenges different from fracturing of typical hard rock. The primary difference is the use of tip-screenout designs and very high sand concentrations to ensure adequate fracture conductivity between the reservoir and the wellbore. Many authors have described tip-screenout fracturing techniques. Although new to the U.S. gulf coast area, hundreds of these treatments have been per formed during the last 2 years. Job sizes ranging from 10,000 to 200,000 lbm of proppant have been pumped successfully from stimulation vessels in the Gulf of Mex ico. Stimulation service companies are gearing up for an increase in demand for this service. The stimulation vessels are equipped with pumping output ratings to 4,000 hydraulic hp, pressure ratings to 15,000 psi, fluid-handling capabilities to 3,000 bbl, above-deck proppant-handling capabilities to more than 200,000 lbm, and blending capabilities to 30 bbl/min at more than 10,000 lbm/min. Applications and Concerns Many reasons exist for applying hydraulic fracturing techniques to friable or unconsolidated sandstone reservoirs. A propped hydraulic fracture can accelerate production from lower-permeability wells and increase recoverable reserves economically. Induced propped fractures also can be used to bypass deep formation damage or to increase vertical flow conformance in higher-permeability applications or laminated reservoirs. The following conditions are candidates for Gulf of Mexico frac-and-pack applications.Reservoirs with significant wellbore damage that historically respond poorly to matrix stimulation techniques. An induced hydraulic fracture can bypass damage and connect the wellbore to the reservoir efficiently, there by reducing skin effects.Poorly consolidated reservoirs that may have fines and sand migration problems. An induced hydraulic fracture can alleviate fines movement by providing a larger high-permeability flow area, which will reduce near-wellbore fluid velocities. Reduced fines migration leads to better cumulative production.Low-resistivity, laminated sand/shale sequences where the connection of the sand lenses to the wellbore through perforations may be limited. An induced hydraulic fracture can provide an effective vertical connection. Sands once thought to be uneconomical in the offshore environment are now becoming attractive because of this new completion method.Low-permeability reservoirs that require a conductive fracture to improve the overall productivity of the zone. P. 226^