Hill Reservoir Research Articles

Characterization of Origin and Evolution of Formation Water in Buried Hill of Jizhong Depression, China, Using Multivariate Statistical Analysis of Geochemical Data

Groundwater samples from buried hill of Jizhong Depression were evaluated using two statistical analyses: hierarchical cluster analysis (HCA) and principal component analysis (PCA). The samples were classified into four clusters, C1–C4, in HCA and the hydrochemical types of C1–C4 are HCO3-Na, Cl·HCO3-Na, Cl-Na, and Cl-Na·Ca. From C1 to C2, C3, and C4, the water-rock interaction becomes increasingly intensive, and rNa/rCl gets lower while total dissolved solids and r(Cl-Na)/rMg get higher. Three components of PCA explain 86.87% of the variance. Component1 (PC1), characterized by highly positive loadings in Na+ and Cl−, is related to evaporation concentration. Component2 (PC2) is defined by highly positive loading in HCO3- and is related to influence of atmospheric water. With high positive loadings in Ca2+ and high negative loadings in Na+ and SO42-, component3 (PC3) suggests plagioclase albitization. The combination of HCA and PCA within the hydrogeological contexts allowed the division of study area into five dynamic areas. From recharge area to discharge area, the influence of atmospheric water gets weaker and water-rock interactions such as evaporation concentration and plagioclase albitization become intensive. Therefore groundwater in buried hill showed paths of hydrochemical evolution, from C1, to C2, C3, and C4. Buried hill reservoir in Jizhong Depression is mainly distributed in hydrodynamic blocking and discharge area; therefore the two regions can be the favorable areas for petroleum migration.

Spatial and inter-annual variability of specific sediment yield: case of hillside reservoirs in Central Tunisia

Water erosion is the major process responsible for soil loss in Central Tunisia. It represents a main risk of sedimentation which threatens the lifetime of water and soil conservation works in the region, such as hillside reservoirs. This paper focuses on the study of spatial and inter-annual variability of specific sediment yield (SSY) estimated from sediment yield (SY) of 23 small watersheds of hill reservoirs located in the Tunisian Dorsal and the Cap Bon regions. The calculated values of mean inter-annual specific sediment yield varied from 180 to 3298 t/km2/year, over a period of 12 years (from 1994 to 2006). The selected catchments were classified into three groups according to their SSY data. The SSY map, elaborated with a geographical information system (GIS), showed an important spatial variability between watersheds of the same group. Moreover, analyses of the coefficient of variation (CV) showed that 70% of the considered sites demonstrate a tendency to moderate and high inter-annual variability of SSY. In order to identify the principal factors governing variability of erosion and sedimentation, a multiple regression analysis was carried out using nine parameters characterizing morphology, topography, land cover, climate and protection works of the 23 considered sites. The generated model revealed that 85% of SSY variability is correlated to seven principal factors, which are drainage area (A), rainfall intensity recorded in 30 min (I30), percentage of water and soil conservation works, percentage of clay and carbonate in soils, vegetation land cover, overall slope index (IG) and rainfall amount (Ra). The obtained SSY results were compared to others cited in a large bibliographical synthesis of studies carried out at the planet scale. We deduced that the SSY values obtained in this study are among the relatively high series in the world. The high variability of specific erosion rates in Central Tunisia is believed to be related to the semi-arid climate, characterized by the irregularity and the severity of storms and the spatial and temporal variability of other multiple factors affecting erosion processes.

Diversity of terrestrial isopods in the northern Tunisian wetlands

AbstractTo evaluate the influence of wetland types on the distribution of terrestrial isopods, species richness, relative abundance and diversity indices were studied in the supralittoral zone of 95 wetlands in the north‐western of Tunisian dorsal, belonging to six types: lagoon, hill reservoir, river, dam, lake and sebkha. We tested the following hypothesis: (i) is isopod diversity influenced by wetland types? (ii) is isopod diversity influenced by bioclimatic zones? and (iii) what are the environmental factors influencing isopod distribution? A total of 3255 individuals belonging to twenty species of terrestrial isopods were captured. Species richness differs significantly between wetland types. A highly significant positive relationship between species richness and both humidity and altitudinal gradient was described. The dendrogram of similarities showed a divergence of the lagoons compared to the remaining wetland types.

A New Gas Injection System for Ultra-Thick Metamorphic Rock Buried Hill Reservoirs

This article proposes a new gas injection system that is a kind of tridimensional gas injection mode applied in the middle-lower part of the reservoir during the process of gas injecting on the reservoir top, which is suitable for the tridimensional reservoir development[1-2]. This system can express the gravity-stable drive effect on the crestal gas injection as well as the effective using of waterflooded wells to form continual micro gas/water slug drive naturally, supply the producing energy timely, diminish the water sealing of waterflooded reservoir matrix, enhance the gas dialysis on fine crack and microscopic sweep efficiency and control the water content, thus improve the production rate and enhance the recovery. Tridimensional gas injection system has been verified by physical simulation and numerical simulation. Pilot testing on Xinggu 7 buried hill reservoir has acquired an actual effect to increase the oil production, boost the pressure and decrease the water cut. Key words: Tridimensional; Gas injection system; Ultra-thick reservoir; Buried hill; Gravity-stable drive; Waterflooded well

The Accumulation Rules of Budate Burial Hill Hydrocarbon Reservoir of Suderte Oilfield in Hailar Basin

Metamorphic rock burial hill reservoir of Beier rift in Hailaer Basin, with large scale reservoir and high output has complex fault system. The fault through going direction roughly is NEE direction, and has wide fault section and lateral quickly changed fault displacement. Metamorphic rock reservoir can be divided into the vertical weathered fracture zone, crack and dissolved pores and caves development belt and tight zone. Accumulation is controlled by hydrocarbon ability of source rock, contacting relationship of source rock and reservoir, oil storage ability of reservoir, and vertical and lateral hydrocarbon migration ability of fault and unconformity surface. And formed top surface weathering crust accumulation pattern which the hydrocarbon migrated laterally along the unconformity surface, and interior reservoir pattern of crack broken zone accumulation which hydrocarbon migrated vertically along fault.

Régime alimentaire et stratégie trophique saisonnière de la Loutre d’Europe, Lutra lutra, dans le Moyen Atlas (Maroc)

Diet and seasonal trophic strategy of the European Otter, Lutra lutra, in Middle Atlas, Morocco. To learn more about the adaptability and predation behaviour of the European Otter (Lutra lutra) in semi-arid regions, its diet has been studied in Wadi Beth, a typical river of Middle Atlas (Morocco), from its source areas (Azrou) to El Kansera hill reservoir dam. Fecal samples (spraints) were systematically collected from six locations during two annual cycles, a collection per season campaign. The study reveals that the otter’s diet is classic (dominant fish), very typical and characteristic of aquatic ecosystems in arid Mediterranean climate, which is reflected in particular by the singular presence of prey like reptiles. Prey species richness totals more than 18 species. Moreover, the frequency of occurrence and relative abundance of taxa consumed were calculated from 2444 identified prey. Fish represent more than 75 % of the prey (relative abundance) with a very large predominance of 3 species of barbels. The anuran amphibians constitute 15 % of the prey. The rest is accounted for, according their respective importance, by insects, ophidians, a chelonian (Mauremys leprosa), birds, crustaceans and finally small mammals. Over time, the diet changed : in autumn 2010, cichlids, introduced into the river, appeared in the prey consumed. The proportion of prey types abruptly changed : perciforms, rare in spring and summer 2010 (less than 4 % of the prey) increased sevenfold in autumn 2010 (27 %) and then declined in the spring and more in summer 2011. In summer 2011, the proportion of barbels dropped, drastically offset by salmonids and, even more, by amphibians. In summer, the proportion of amphibians and ophidians becomes more important. Site variations are linked to local conditions : presence of ponds, nature of the bottom, slope, speed and flow of the water, etc. Finally, small-sized fish (salmonids and barbels) dominate the diet : 80 % are less than 10 cm.

Experimental and Simulation Study of Complex Structure Well Pattern Optimization for Buried Hill Fractured Reservoirs

The use of a vertical well pattern results in productivity deficiency and poor development effect when developing buried hill reservoirs with complex properties. In this work, experiments are conducted to determine the best pattern for complex structure wells in buried hill reservoirs. Discretization is employed in an experimental method that uses unit cubic rocks with a size of 5 cm × 5 cm × 5 cm. The rocks are bonded in a spotty or reticular design to form a macroscopic model. Based on water flooding similarity criteria of fractured reservoir, an experimental model similar to a quarter of a five-spot unit in an actual reservoir is designed and manufactured. By selectively plugging wells in the model, various well patterns are established. Simulation results indicate that the vertical–vertical well pattern exhibits the fastest water breakthrough, fastest increase in water cut, and lowest recovery under the same pressure difference and well spacing. The horizontal–horizontal well pattern has the slowest water cut increase and the highest final oil recovery. For fishbone wells, this pattern facilitates an ideal development effect when the percolation direction is perpendicular to the plane determined by the mother bore and branch. When liquid rate, water cut, and recovery are considered, the horizontal–horizontal well pattern is recommended when conditions allow.

Beier Depression Petroleum System Study in Hailaer

Through the study of Beier depression accumulation critical moment, divided into three sets of petroleum system in beier depression: passive faulted depression primary petroleum system, active faulted depression primary petroleum system and fault depression transform secondary petroleum system. Through the typical reservoir oil-water distribution rule and reservoir dissect result can get to know oil and gas of Beier depression concentration distribute in passive faulted depression sequence petroleum system, mainly develop reverse fault block reservoir as well as buried hill reservoir blocked by fault and uncomformable surface, active faulted depression sequence petroleum system mainly develop structure and fault-lithologic composite reservoir; Secondary petroleum system mainly develops fault lithologic reservoir; Secondary petroleum system and primary petroleum system ‘complementary’ distribution of oil and gas. Through the petroleum system classification, to find the distribution regularity of oil and gas, and guide field work.

A water balance approach for quantifying subsurface exchange fluxes and associated errors in hill reservoirs in semiarid regions

AbstractHill reservoirs are rain water‐harvesting structures that have been increasingly adopted in arid and semi‐arid regions, such as North Africa, to capture and conserve runoff water and for use as alternative water resources in agricultural development. Currently, process‐based information on reservoir hydrology is needed to improve reservoir management practices.The study aims to develop an approach to estimate the reservoir–subsurface exchange flux and its associated error at the annual, monthly, and intra‐monthly time scales to better understand the hydrological functioning and dynamics of hill reservoirs. This approach is based on a hydrological water balance of the hill reservoir by considering all water input and output fluxes and their associated errors.The results demonstrate the ability and relevance of the approach in estimating the net reservoir–subsurface exchange flux and its error estimations at various time scales. Its application on the Kamech catchment (Northern Tunisia) for the 2009–2012 period demonstrates that the net reservoir–subsurface exchange flux is positive, i.e. the infiltration from the hill reservoir to the aquifer dominates over the discharge from the aquifer to the reservoir. Moreover, reservoir–subsurface exchange constitutes the main output component in the water balance. Copyright © 2014 John Wiley & Sons, Ltd.

Reservoir Characteristics of Buried Hill and Oil and Gas Distribution of Hailaer Basin - Case Study of Budate Formation of Sudeerte Oilfield

Buried hill reservoirs are typically found in Sudeerte oilfield in Hailaer basin. In this paper, the lithology, physical property and electric property of buried hill reservoirs are studied incorporating core data, mud logging, wireline logging and seismic attributes data. The major reservoir types of Budate buried hill are confirmed to include porosity, fracture, cavern and dissolved pore, which belong to dual porosity reservoirs. Vertically, the reservoirs get worse with the increase of buried depth and are controlled horizontally by weathering crust position and tectonic stress, and locations nearby fractured belt and structural high positions are preferable places for the formulation of good reservoirs. Oil and gas within the reservoir mainly accumulated inside fractures and pores and reservoirs with plenty existence of fractures and pores have good oil and gas shows and vice versa.

Mesh Generation for 3D Geological Reservoirs with Arbitrary Stratigraphic Surface Constraints

With the advanced field observation, image and drilling technology, geological structure of reservoirs can be described in more details. A novel 3D mesh generation method for geologica l reservoir mode ls is proposed and imple mented with arbitra ry stratigraphical surface constraints, which ensures the detailed geologica l structure and materia l properties are well described and analysed. Specifica lly, the stratigraphic interfaces a re firstly e xt racted and meshed, and then the tetrahedron mesh is generated with the constraints of the meshed surfaces. The proposed approach includes the following five steps: (1) e xtract ing stratum interfaces; (2) creat ing a background mesh with size field on the interfaces; (3) constructing geodesic isolines fro m the interface boundaries to the interior; (4) e mp loying a geodesic - based approach to create triangles on the area between adjacent isolines and to combine the m together; (5) generating tetrahedron mesh for 3D reservoirs with constraints of the above surface triangular mesh. Th is approach has been imple mented and applied to the La wn Hill reservoir model to demonstrate its effectiveness and usefulness.

Hill lakes: innovative approach for sustainable rural management in the semi-arid areas in Tunisia

<p>In Tunisian semi-arid regions, where water is a rare commodity and the large dams cannot be justified considering the very limited water contributions and the very high evapotranspiration, innovative techniques of harvesting water have been adopted. Tunisia has initiated a policy of small dam construction aiming to combine land and water management with socioeconomic development. They also target erosion control and protection of downstream infrastructure. Integrated rural development is achieved through the provision of a scarce but vital renewable resource. Using the results of multi-disciplinary research carried out in a network of 25 hill lakes implemented in a semi-arid area, the present article shows the role of small dams in the mobilization and management of water and soil resources. The issues involved in integrated development around hill reservoirs are closely linked to the sustainability of water. The agricultural development must be adapted to the life expectancy of the dam and the availability of water in dry periods. The recharge of the groundwater in the aquifers improves the potential for development. However, the impact of the stored water on health must be studied. The environmental impact of the lake structures is linked to the quality of the water and the maintenance of its supply.</p>

Numerical Simulation of the Buried Hill Reservoir in Bohai Bay

Buried hill reservoir fracture description and reservoir simulation technology have been a hot research, but also is one of the key issues that restrict the efficient development of such reservoirs. Based on JZ buried hill reservoir which heterogeneity is strong, some wells water channeling fast and difficult to control the situation for fracture affect, a typical block of dual medium reservoir numerical models which was comprehensive variety of information, discrete fracture characterization and geological modeling is established. The fractured reservoir numerical model is simulated through Eclipse software to seek the law of remaining oil distribution. Through the reservoir geological reserves and production history matching, the remaining oil distribution of main production horizon is forecasted. On this basis, the results of different oilfield development adjustment programs are predicted by numerical simulation.

Origin and accumulation of high-maturity oil and gas in deep parts of the Baxian Depression, Bohai Bay Basin, China

Great quantities of light oil and gas are produced from deep buried hill reservoirs at depths of 5,641 m to 6,027 m and 190 °C to 201 °C in the Niudong-1 Well, representing the deepest and hottest commercial hydrocarbons discovered in the Bohai Bay Basin in eastern China. This discovery suggests favorable exploration prospects for the deep parts of the basin. However, the discovery raises questions regarding the genesis and accumulation of hydrocarbons in deep reservoirs. Based on the geochemical features of the hydrocarbons and characteristics of the source rocks as well as thermal simulation experiments of hydrocarbon generation, we conclude that the oil and gas were generated from the highly mature Sha-4 Member (Es4) source rocks instead of thermal cracking of crude oils in earlier accumulations. The source kitchen with abnormal pressures and karsted carbonate reservoirs control the formation of high-maturity hydrocarbon accumulations in the buried hills (i.e., Niudong-1) in conjunction with several structural-lithologic traps in the Es4 reservoirs since the deposition of the upper Minghuazhen Formation. This means the oil and gas exploration potential in the deep parts of the Baxian Depression is probably high.

Geochemical and isotopic study of surface and groundwaters in Ain Bou Mourra basin, central Tunisia

A comprehensive study of the hydrogeological framework and groundwater resources using chemical and isotope methods was recently carried out in the Ain Bou Mourra basin (central Tunisia). In this area, surface water in rivers is seasonal, and therefore groundwater is the perennial source of water supply for domestic and agricultural purposes. A great dam and several harvesting features have been built within a national water management strategy in order to increase the overall water availability in the basin.In this study, groundwaters from the Paleogene–Neogene formations in the Ain Bou Mourra together with rain and surface waters have been analyzed in order to investigate the mineralization processes, water origin and recharge sources. Chemical data indicate that surface and groundwater samples show a large spatial variability of chemical facies. Most of the groundwaters are slightly to moderately mineralized and are of Ca–Mg–Cl–SO4 water type, induced mainly by feldspar and silicate weathering, dissolution of evaporitic and carbonate minerals and cation exchange reactions.Data inferred from 18O and deuterium isotopes in groundwater samples indicated recharge with modern rainfall. Water characterized by lower δ18O and δ2H values is interpreted as recharged by non-evaporated rainfall originating from Mediterranean air masses at higher altitude. However, water with relatively enriched δ18O and δ2H contents is thought to reflect the occurrence of an evaporation process related to the long term practice of flood irrigation.The investigated surface water samples collected from the dam, river, hill reservoirs and pumped-storage water power plant are affected by a significant evaporation and reveal large seasonal variations which could be controlled by the water volume changes in the open surface reservoirs and the meteorological conditions during evaporation, condensation and precipitation.Considerable tritium concentration in groundwaters allowed qualitative identification of the present day component. It is assumed that this component is supplied by recent precipitation at the Oligocene–Miocene outcrops of the study area.Data revealed the existence of high 14C activities in groundwaters. Reservoir of dissolved carbon is simultaneously depleted in 13C, reflecting the domination of CO2 produced by C4 plants in formation of carbonate mineralization of analyzed waters.

Analysis of Fault Characteristics and Reservoir Forming Control in Middle Fault Depression Belt in Hailer-Tamtsag Basin

In order to reveal in middle fault depression belt of Hailer-Tamtsag Basin buried hill oil and gas migration and accumulation characteristics, we summarize controlling effect of fault on oil and gas migration and accumulation of buried hill, which by analysing genetic mechanism of buried hills based on fault systems formation and evolution. Research shows that three types of fault system in Hailer-Tamtsag Basin: early stretched fault system(Type I), early stretched middle tensile shearing fault system(Type I-II), early stretched middle tensile shearing reverse late fault system(Type I-II-III). Type I-II and I-II-III are stretching by NW tensional stress in Nantun group ,which afford tectonic framework for syngenesis buried hill and epigenetic buried hill. Type I make buried hills complicated .It is also favorable to ancient geomorphological buried hill in the fault less affected zones. Although they formed cracks dense zone easier, Type I-II and I-II-III fault system damage the reservoir which is not conducive to " hydrocarbon-supplying window " formation; Type I fault system have less promotion on the development of the buried hill reservoir, while it is conducive to hydrocarbon accumulation as the block boundary in buried hill hydrocarbon. Fault formed source rocks two kinds for hydrocarbon mode: unidirectional and bidirectional, which formed two reservoir-forming pattern: Unidirectional transportation hydrocarbon of weathering crust or hydrocarbon of fracture damage zones and bidirectional transportation hydrocarbon of weathering crust or hydrocarbon of fracture damage zones.

The Controlling Effect of Unconformity Structure on Hydrocarbon Accumulation

Based on lots of previous studies, the unconformity structure characteristics were studied and the controlling effect of unconformity structure on hydrocarbon reservoir, migration path and oil-gas reservoir type were analyzed. The result shows that the unconformity structure is composed of upper basal conglomerate layer, lower weathering clay layer and semi-weathering rock; the interlocking pores in basal conglomerate layer and pore-cave-fracture system in semi-weathering rock are the main storage space of hydrocarbon reservoir; And hydrocarbon migrates laterally through capillary “channeling effect” in interlocking pores, and the pore-cave-fracture system in semi-weathering rock is an important path for hydrocarbon migration laterally and vertically; stratigraphic overlap hydrocarbon reservoir and stratigraphic unconformity reservoir are the two type of reservoirs related to unconformity, and buried hill reservoir is an important type of the latter.

A New Technique: Fishbone Well Injection

As a new developing method, fishbone well injection has been used in buried hill reservoirs. Based on numerical simulation, optimization research on the new reservoir developing method, which means fishbone wells injecting water at the bottom and horizontal wells producing oil at the top, is present. Compared with horizontal well injection, the results show that the fishbone well can increase the control area, form planar flooding, and hold the injection water upward slowly and evenly. The reasonable fishbone well parameters, such as branching angle, branch number, and branch length, are obtained. The fishbone well injection provides a new technical method for developing buried hill reservoirs efficiently.

The Cognition Decide the Exploration- The Exploration Study on Buried Hill Reservoir in the Liaohe Basin

In recent years the buried hill exploration was a main power for increasing reserve& production in the Liaohe oil field. By the research and analysis on the buried hill reservoir exploration in the Liaohe oil field in the paper, It point out that the previously mistake cognition was broken through in the buried hill reservoir exploration with the seismic, logging etc. technology development. The achievement list as: 1. The conclusion is drawn about the depth of the buried hill reservoir determined by the depth of the source rock which clarified the mistake about the buried hill reservoir formed only in the shallow formation. 2. The inner of the buried hill reservoir of the metamorphic rock is a fissure-cave system formed by the various and layered rocks which served as an oil accumulation place which broke through the cognition on no pore in the deep inner of the buried hill reservoir. 3.The reservoir-formed pattern is built on the study of the controlled factor in the buried hill reservoir which denied the barrier of the basalt layer for oil and gas translation over the buried hill reservoir .In this paper by the summary of the cognition breakthrough and achievement, it shows the next exploration direction in buried hill reservoir in the Liaohe depression.

Research and Application of the Deep Horizontal Drilling and Completion Technology for Liaohe Oilfield Buried Hill Reservoir

With the depletion of shallow-layer oil and gas pools inLiaohe oilfield, buried hill stratigraphic reservoirs in Liaohe oil field are becoming main objectives for exploration in recent years, especially in high-risk areas of Xinglongtai deep the Hing ancient buried hill resources are particularly rich. Since 2007, Liaohe oilfield increased investment for Buried Hill reservoirs with deep horizontal drilling developt the buried hill reservoir. Liaohe has completed 36 deep horizontal, with a total footage of 183920m, the average depth of 5109m. Improving drilling speed of "buried hill deep horizontal and branch horizontal wells”, and reducing drilling costs are of great urgency. “Hing buried hill deep horizontal, horizontal wells,” with composite drilling technology, supporting the optimization of PDC bits, the high-pressure jet drilling, the MWD borehole trajectory control and optimization of drilling parameters, the new drilling fluid technology and so on. With a large number of horizontal wells put into Buried Hill stratigraphic reservoirs, oil and gas production of average deep horizontal well increase of 2-5 times. Besides, the previous recovery and production of oil and gas reservoirs significantly improved to create an objective economic and social benefits.