Reservoir Properties

Carbonate rocks are not normally transported over long distances, and we find carbonate reservoir rocks mostly at the location of origin, in situ . They are usually the product of marine organisms. However, carbonates are often severely affected by diagenetic processes. A more detailed description of altered carbonates and their reservoir properties is given below in the description of diagenesis . 

The number of injectors required may be estimated in a similar manner, but it is unlikely that the exploration and appraisal activities will have included injectivity tests, of say water injection into the water column of the reservoir. In this case, an estimate must be made of the injection potential, based on an assessment of reservoir quality in the water column, which may be reduced by the effects of compaction and diagenesis. Development plans based on water injection or natural aquifer drive often suffer from lack of data from the water bearing part of the reservoir, since appraisal activity to establish the reservoir properties in the water column is frequently overlooked. In the absence of any data, a range of assumptions of injectivity should be generated, to yield a range of number of wells required. If this range introduces large uncertainties into the development plan, then appraisal effort to reduce this uncertainty may be justified. 

The flowrate of oil into the wellbore is also influenced by the reservoir properties of permeability (k) and reservoir thickness (h), by the oil properties viscosity (p) and formation volume factor (BJ and by any change in the resistance to flow near the wellbore which is represented by the dimensionless term called skin (S). For semisteady state f/owbehaviour (when the effect of the producing well is seen at all boundaries of the reservoir) the radial inflow for oil into a vertical wellbore is represented by the equation ... 

The first term (AQ) is the pressure drop due to laminar flow, and the FQ term is the pressure drop due to turbulent flow. The A and F factors can be determined by well testing, or from the fluid and reservoir properties, if known. 

The exact relationship will depend upon both fluid and reservoir properties, and will be investigated during well planning. 

Drawdown and build-up surveys are typically performed once a production well has been completed, to establish the reservoir property of permeability (k), the well completion efficiency as denoted by its skin factor (S), and the well productivity index (PI). Unless the routine production tests indicate some unexpected change in the well s productivity, only SBHP surveys may be run, say once a year. A full drawdown and build-up survey would be run to establish the cause of unexplained changes in the well s productivity. 

Primary production typically recovers 10—25% of the oil originally ia the reservoir. Efficiency of primary production is related to oil properties, reservoir properties, geometric placement of oil wells, and the drilling and completion technology used to drill the wells and prepare them for production. Pumping the well can maintain production at economic levels for years. 

Petroleum and chemical engineers perform oil reservoir simulation to optimize the production of oil and gas. Black-oil, compositional or thermal oil reservoir models are described by sets of differential equations. The measurements consist of the pressure at the wells, water-oil ratios, gas-oil ratios etc. The objective is to estimate through history matching of the reservoir unknown reservoir properties such as porosity and permeability. 

ABSTRACT CO2-ECBM Micro-Pilots have been carried out in Canada and China to assess the response of low- and high-rank coal reservoirs to C02 injection. The selectivity of coals for C02, compared to methane, can vary from 10 to 1 depending on coal rank. Although the C02 is more efficiently stripped by coals of low rank, permeability impairment is greater and the amount of methane recovered is less than for high-rank coals, providing other reservoir properties are similar. If a pure C02 source is not available, N2-C02 mixtures may produce more favourable economics. 

Other reservoir properties being similar, high-rank coals are more favorable for C02 storage because of their methane displacement efficiency (related to lower sorption selectivity for C02 compared to methane and higher absolute sorption of methane with increasing rank see Figs 1 and 3). Higher ranks of coal are also more... 

FIGURE 3.7 Diagram showing effects of sedimentary structures and textures on the flow of fluids in a point-bar sandstone reservoir. The cross-bedded unit is coarser grained and is inferred to have better reservoir properties (i.e., permeability) than the overlying rippled unit (A). Uneven advance of injected fluids illustrating permeability variations results from differences in reservoir quality. (Modified after Ebanks, 1987.)... 

The behavior of liquids in narrow tubes is one of the most common examples in which capillary forces are involved. It will be shown later how important this phenomenon is in many different parts of everyday life and technology. In fact, liquid curvature is one of the most important physical surface properties that requires attention in most of the application areas of this science. The range of these applications is from blood flow in the veins to oil recovery in the reservoir. Properties of fabrics are also governed by capillary forces (i.e., wetting, etc.). The sponge absorbs water or other fluids where the capillary forces push the fluid into the many pores of the sponge. This is also called wicking process (as in candlewicks). 

Secondary porosity results from the dissolution of carbonates in the subsurface environment. It can occur both in limestones and in sandstones where carbonate cements of original labile detrital minerals are dissolved. Because the formation of secondary porosity can substantially enhance the reservoir properties of sediments, it has received considerable attention from the petroleum industry. 

Scheme 5. The peralkylation or perfunctional-ization reaction this reaction is made possible by the proton-reservoir property of the starting organometallic cation (see Schemes 2 and 3) and is spontaneously reproduced by iteration many times until a steric limit is reached a) hexa-substitution compounds are formed with methyl...

The challenge is therefore to find a theoretical expression for these scaling laws. It will in any case depend upon scaling laws for the statistical distribution of fundamental geometrical reservoir properties. It will also depend upon these hidden processes that arise because of the nonlinear nature of movable boundary flows (quite apart from nonlinearities intrinsic to the continuum relations themselves). There have been some remarkable pioneering attempts to predict continuum properties of porous media from fundamental parameters, mainly by chemical engineers (of whom I wish to single out Howard Brenner and co-workers) and physicists, but they have as yet made little impact on the oil industry. 

Although not included in this paper, a field experiment has been designed for the Kern River Unit located at the edge of the Kern River field, Kern County, California. The ideal emulsification properties of the crude oil have already been discussed in this paper. This field is an example of reservoir properties that should be considered ideal when selecting a reservoir for future testing of the process heterogeneous production zones, areas of low and high oil saturations, low salinity, low clay content, and crude oil that is easily emulsified. 

In the preceding section, we have shown the electron-reservoir properties of the redox series [Fe(/7 -C5R5)( 7 -C6Me6)] / / on the reduction side with the neutral 19-electron Fe form. The 17-electron dicationic Fe form can be isolated as the SbXfi salts (R = Me, X = F or Cl)) and used as very strong oxidants, with a stan-... 

Hesse R. and Abid I. A. (1998) Carbonate cementation—the key to reservoir properties of four sandstone levels (Cretaceous) in the Hibernia oil field, Jeanne d Arc Basin, Newfoundland, Canada. In Carbonate Cementation in Sandstones Distribution Patterns and Geochemical Evolution (ed. S. Morad). International Association of Sedimen-tologists, Oxford, vol. 26, pp. 363-394. 

In order to verify the dynamic concept of the behavior of gas throughout sedimentary basins, we first report the results of an empirical study on The Netherlands offshore gas fields (Broad Fourteens Basin, Fig. 1 shadowed area). This basin is part of the European Upper Carboniferous Basin. The gas fields are sourced from Upper Carboniferous coals and shales, reservoired in Upper Permian Zechstein carbonates (Plattendolomit) and sealed by Zechstein rock salt (Na2-4). The problem facing exploration was that the rate of dry holes was very high even if structural closure and favorable reservoir properties were confirmed. In order to find a solution and to offer a tool for the prediction of fill or non-fill of structures before drilling, we examined 29 case histories (fields, finds, shows and dry holes) under the aspect of dynamics of gas flow. 

Bjprlykke, K, Aagaard, P., Dypvik, H., Hastings, D.S. and Harper, A S. 1986. Diagenesis and reservoir properties of Jurassic sandstones from the Haltenbanken Area, offshore mid Norway. In E. Holter, A M. Spencer, C.J. Campbell, S.H. Hanslien, P.H.H. Nelson, E. Nysaether and E.G. Ormaasen (Editors), Habitat of Hydrocarbons on the Norwegian Continental Shelf. Graham Trotman, London, pp. 275-286. 

Interestingly, the electron reservoir properties of redox active ligands are also found to be useful to impose one-electron transformation on late transition metals. Rhenium complexes are known to be powerful oxo-transfer reagents [27]. However, closed-shell... 

Scheme 8 Electron-reservoir properties of redox active ligands assisting in activation...

In order to test the functionality and reservoir properties of the new tethered lipid bilayers, the ion carrier valinomycin was used to study the selective transport of potassium ions. The data, shown in Table 1, confirmed the formation of a fluid and insulating tBLM. The addition of 0.1 M potassium ions resulted in a drop in resistance of up to three orders in magnitude corresponding well to literature values [13],... 

Carbonate cements either indirectly enhance or deteriorate the reservoir properties of sandstones. Enhancement of reservoir properties occurs when (i) appreciable volumes of carbonate cements are dissolved, causing the formation of secondary porosity and (ii) small amounts of carbonate cement are evenly distributed in the sandstones to support the overburden weight and prevent the collapse of framework grains and consequent elimination of primary porosity. Souza et al. (1995) demonstrated that a few per cent of dolomite cement is sufficient to prevent the collapse of Aptian reservoir sandstones from Brazil despite the high content of ductile lithic fragments. 

The scales of carbonate redistribution, and thus reservoir quality enhancement, are difficult to constrain. Several workers have argued that the reservoir properties of sandstones are greatly enhanced due to large-scale carbonate dissolution (Lonoy et al., 1986 Schmidt McDonald, 1979). As the undersaturated waters have to circulate through large volumes of permeable sediment to cause economically important carbonate cement dissolution, it is expected that such secondary porosity develops in partially rather than pervasively cemented sand-... 

Effect of dolomite cement upon the reservoir properties of the Chaunoy Formation sandstone... 

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