Connation

Poorly sorted sediments comprise very different particle sizes, resulting in a dense rock fabric wifh low porosify. As a resulf the connate water saturation is high, leaving little space for the storage of hydrocarbons. Conversely, a very well sorted sediment will have a large volume of space between the evenly sized components, a lower connate water saturation and hence a larger capacity to store hydrocarbons. Connate water is the water which remains in the pore space after the entry of hydrocarbons. 

Solution gas drive occurs in a reservoir which contains no initial gas cap or underlying active aquifer to support the pressure and therefore oil is produced by the driving force due to the expansion of oil and connate water, plus any compaction drive.. The contribution to drive energy from compaction and connate water is small, so the oil compressibility initially dominates the drive energy. Because the oil compressibility itself is low, pressure drops rapidly as production takes place, until the pressure reaches the bubble point. 

Gas reservoirs are produced by expansion of the gas contained in the reservoir. The high compressibility of the gas relative to the water in the reservoir (either connate water or underlying aquifer) make the gas expansion the dominant drive mechanism. Relative to oil reservoirs, the material balance calculation for gas reservoirs is rather simple. A major challenge in gas field development is to ensure a long sustainable plateau (typically 10 years) to attain a good sales price for the gas the customer usually requires a reliable supply of gas at an agreed rate over many years. The recovery factor for gas reservoirs depends upon how low the abandonment pressure can be reduced, which is why compression facilities are often provided on surface. Typical recovery factors are In the range 50 to 80 percent. 

The above experiment was conducted for a single fluid only. In hydrocarbon reservoirs there is always connate water present, and commonly two fluids are competing for the same pore space (e.g. water and oil in water drive). The permeability of one of the fluids is then described by its relative permeability (k ), which is a function of the saturation of the fluid. Relative permeabilities are measured in the laboratory on reservoir rock samples using reservoir fluids. The following diagram shows an example of a relative permeability curve for oil and water. For example, at a given water saturation (SJ, the permeability... 

D, 8 0 and Cl concentration data suggest the mixing of meteoric water, connate seawater and magmatic gas (Seki, 1991) (Fig. 2.20). Br/Cl and B/Cl ratios are different from those of seawater (Fig. 2.21). This difference and N2-H2-Ar gas composition indicate a contribution of magmatic gas (Seki, 1991, 1996). 

The specific microbes used depends on many factors, for example, the particular formation involved, the specific hydrocarbons in the formation, and the desired microbial action on these formation hydrocarbons. The microbes may be aerobic or anaerobic and may or may not require one or more additional nutrients (e.g., naturally ocurring or injected) to be included in the formation. Highly mobile microbes, such as flagellated or ciliated bacilli, are useful. The microbes are sized so that they are mobile in the connate water of the formation [966]. 

Formation damage caused by clay migration may be observed when the injected brine replaces the connate water during operations such as water-flooding, chemical flooding including alkaline, and surfactant and polymer processes. These effects can be predicted by a physicochemical flow model based on cationic exchange reactions when the salinity decreases [1665]. Other models have also been presented [345,1245]. 

Epithermal Low temperatures (< 300 °C) and pressures, farthest from the intrusive, mixed with connate and meteroric waters Gold, silver, mercury, antimony, arsenic, bismuth, selenium, lead, zinc... 

Telethermal Essentially meteoric and connate waters with little addition of magmatic water, very low temperatures (< 100 °C) and pressures, near the surface Lead, zinc, cadmium germanium... 

The Eh of connate waters (water entrapped in the interstices of sediment at the time of deposition) ranges from 0 to -200 mV. For example, formation water from two monitoring wells in the lower limestone of the Florida aquifer near Pensacola ranged from +23 to -32 mV,67 and formation fluids from a Devonian limestone in Illinois used for injection at a depth of about 3200 ft had an Eh of -154 mV.16... 

Effect of Ca2. In many reservoirs the connate waters ontain substantial quantities of divalent ions (mostly Ca . In alkaline flooding applications at low temperatures, the presence of divalent ions leads to a drastic increase in tensions r35,36]. Kumar et al. f371 also found that Ca and Mg ions are detrimental to the interfacial tensions of sulfonate surfactant systems. Detailed studies at elevated temperatures appear to be non-existent. 

Crude Oils and Connate Water. The multiple micellar slug process was developed for the tertiary recovery of three light oils viz. Bradford crude, Bonnie Glen crude and Provost crude. The viscosities and densities of the three crude oils used are listed in Table I. 

A 2% (w/v) sodium chloride solution was used as the connate water in all corefloods. It should be mentioned that it is desirable to incorporate divalent cations, such as Ca++ and Mg++, in the slug formulations as well as in the connate water to simulate an actual reservoir. 

For the wet case, the foam enters and achieves steady state after several pore volumes. A mobility reduction compared to water of about 90% ensues. However, for the dry case, there is about a one pore-volume time lag before the pressure responds. During this time, visual observations into the micromodel indicate a catas-tropic collapse of the foam at the inlet face. The liquid surfactant solution released upon collapse imbibes into the smaller pores of the medium. Once the water saturation rises to slightly above connate (ca 30%), foam enters and eventually achieves the same mobility as that injected into the wet medium. 

The human leukodystrophies are inherited disorders of central nervous system white matter. These disorders are characterized by a diffuse deficiency of myelin caused by a variety of genetic lesions and often manifest before 10 years of age (Table 38-1). Some are caused by mutations in the PLP gene and resemble the PLP animal mutants described in Chapter 4 [ 1,23]. As with the animal models, depending on the nature of the mutation, they vary from a severe form in connatal Pelizaeus-Merzbacher disease (PMD) through an intermediate phenotype in classical PMD to a mild phenotype in spastic paraplegia. It is noteworthy that some mutations of the PLP gene also cause a peripheral neuropathy [24], very probably related to the expression of low levels of PLP in peripheral nerve (see Ch. 4). 

Pelizaeus-Merzbacher disease (classical and connatal forms) and spastic paraplegia X-linked PLP Variable hypomyelination due to different mutations in the major structural protein of CNS myelin similar to rodent mutants such as the jimpy mouse 1,23... 

The chloride content of groundwater may be a sensitive indicator of either the distance between the intake area of the aquifer and coast or the amount of evapotranspiration prior to groundwater recharge. Because chloride is not normally derived from dissolution of solid aquifer materials and it does not enter into ion exchange reactions to any great extent, the chloride content in shallow aquifers and aquifers isolated from sources of connate water should reflect some of the original environmental factors of the outcrop area [19,86]. 

Oxygen and hydrogen isotopes are a powerful tool in the study of the origin of subsurface waters. Prior to the use of isotopes, it was generally assumed that most of the formation waters in marine sedimentary rocks were of connate marine origin. This widely held view was challenged by Clayton et al. (1966), who demonstrated that waters from several sedimentary basins were predominantly of local meteoric origin. 

Presently, in the view of numerous subsequent studies, (i.e., Hitchon and Friedman 1969 Kharaka et al. 1974 Banner et al. 1989 Connolly et al. 1990 Stueber and Walter 1991), it is obvious that basin subsurface waters have complicated histories and frequently are mixtures of waters with different origins. As was proposed by Knauth and Beeunas (1986) and Knauth (1988), formation waters in sedimentary basins may not require complete flushing by meteoric water, but instead can result from mixing between meteoric water and the remnants of original connate waters. 

Beny JL, Connat JL An electron-microscopic study of smooth muscle cell dye coupling in the pig coronary arteries. Circ Res 1992 70 49-55. 

Rennick RE, Connat JL, Burnstock G, Rothery S, Severs NJ, Green CR Expression of connexin 43 gap junctions between cultured vascular smooth muscle cells is dependent upon phenotype. Cell Tissue Res 1993 271 323-332. 

The carbonaceous and nitrogenous components in peat and in the connate waters were determined by Motojima (13) and Maki (12) and the results are given in Tables IX and X. The relationship between the ratios of Total C/ Total N of peat and those of the connate waters suggests that the same micro-... 

Table X. Vertical Variation of Carbon and Nitrogen of Connate Waters in Peat from Higashiyonesato ...

Leaves never gland-dotted stamens often connate into a tube.Order Meliales... 

Perianth usually composed of similar or subsimilar segments in two or one series, usually very conspicuous and petaloid and if united then connate in the lower part into a single tube, but if perianth of separate calyx and corolla then the branches modified into cladodes or else herbs or woody climbers or shrubs with one-celled ovary and six stamens or perianth dry and fruit dehiscent or else stamens three, two, or one on a column. 

Water invariably occurs with petroleum deposits. Thus, a knowledge of the properties of this connate, or interstitial, or formation water is important to petroleum engineers. In this chapter, we examine the composition of oilfield water water density, compressibility, formation volume factor and viscosity solubility of hydrocarbons in water and solubility of water in both liquid and gaseous hydrocarbons and, finally, water-hydrocarbon interfacial tension. An unusual process called hydrate formation in which water and natural gas combine to form a solid at temperatures above the freezing point of water is discussed in Chapter 17. 

CONNATE WATER. Water that is trapped in marine sediments at the time they are laid down in the sea is commonly called commie Hater. As the term implies, connate water is produced at the same lime as the rock and constitutes a sort of fossil seawater. 

Many geological processes may have modified the composition of connate brines to produce iheir wide range. Obviously these alterations have been extensive. Some connate waters are essentially saturated... 

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