Reservoirs water sensitivity

The atmosphere is an important conveyor belt for many pollutants. The atmosphere reacts most sensitively to anthropogenic disturbance because proportionally it represents a much smaller reservoir than land and water furthermore, the residence times of many constituents of the atmosphere are smaller than those that occur in the other exchange reservoirs. Water and atmosphere are interdependent systems. Many pollutants, especially precursors of acids and photooxidants, originate directiy or indirecdy from the combustion of fossil fuels. Hydrocarbons, carbon monoxide, and nitrogen oxides released by thermal power plants and, above all by automobile engines, can produce, under the influence of sunlight, ozone and other photooxidants. 

The manner of injection of the C02 is often at question. When no mobility-control additive is used, the choice is usually between continuous C02 injection and the so-called WAG (water alternated with gas) method. Continuous C02 injection method is generally used only when the reservoir is very tight or water-sensitive, so that water could be injected only at an uneconomically low rate. WAG was originally suggested by Caudle and... 

Effect of pH. The pH of the flowing fluid is an important factor in the fines migration process (5, 12, 52, 58). Mungan (52) noted that injection of strong acids or bases could cause permeability damage. Under very high or very low pH conditions, the permeability damage is caused by dissolution of the matrix material, which produces fine particles of varied mineral composition. Somerton et al. (58) found that the water sensitivity of reservoir sands was related to the pH response exhibited by the rock after the contact with fresh water. Most sandstone cores showed an increase in the effluent pH after the switch was made... 

Abstract Chalk is the constituent material of numerous oil reservoirs in North Sea. The mechanical behaviour of a saturated chalk has been largely studied. However, different aspects of its behaviour are not yet well understood material characteristics depend on the saturating fluids and chalk response is time-dependent. This paper proposes the PASACHALK numerical model an elasto-plastic constitutive law is presented, which reproduces the different plastic mechanisms of the chalk (pore collapse and shear failure) and the influence of pore fluids. The water sensitivity of this soft rock is explained by the existence of suction effects in chalk. Finally, a simulation of a hypothetical reservoir is proposed to show the response of the elasto-plastic model during depletion phase and water injection phase. 

While water sensitivity was initially realized during the water flooding of petroleum reservoirs, it is now of serious concern in many other areas. It has been found that attempts to acidize wells with aqueous solutions of HCl and HF have resulted in failure due to a drastic permeability decrease near the well bore. Water sensitivity is also believed to be a cause of long term permeability decreases found in gas wells especially in the spring, due to the presence and movement of low salinity water. Although this phenomenon was discovered as early as the year 1945 (1), up until now mathematical models describing the water sensitivity phenomenon have not been put forth. Understandably, such a model is required to predict the phenomenon quantitatively and can be helpful in the design of preventive measures. 

Table A-9. Wellbore cleanup/damage removal for oil wells Low reservoir pressure, water-sensitive sand (used in the Netherlands)...

Dodd, C. G., F. R. Conley, and P. M. Barnes, 1954. Clay minerals in petroleum reservoir sands and water sensitivity effects. Proc, 3rd Nat. Conf, Clays Clay Min. 221. 

Sensitive analytic procedures enable detection and measurement of very low tracer levels. In tracer studies, an identifiable tracer material is injected through one or more injection wells into the reservoir being studied. Water or other fluid is then injected to push the tracer to one or more recovery wells in the reservoir. The output of the recovery wells is monitored to determine tracer breakthrough and flow through the recovery wells. Analysis of the breakthrough times and the flows yields important information regarding how to perform the secondary or enhanced recovery processes. 

A sensitive and selective method, which is specific for oxamyl and may be applicable to other oxime carbamates and their metabolites in heavily polluted waters, involves the use of HPLC/MS/MS. A 75-mL reservoir is attached on top of a Bond-Elut SAX (l-g/6-mL) (Varian), which is connected to an Oasis HLB (l-g/20-mL)... 

The methods described above were tested at two sites in Hawaii The Nuuanu reservoir on Oahu, which is above downtown Honolulu, and the Waikoloa Dam on Hawaii Island, which is above the town of Waimea. In both cases the analyses were performed with and without topographic data obtained by a field survey crew. Detailed results from the ca e studies and results of a sensitivity analysis are reported elsewhere. The flood inundation maps produced for Waimea and Honolulu were overlaid onto several GIS infrastructure layers. These layers included major roads, secondary roads, schools, nursing homes, hospitals, police stations, fire stations, civil defense headquarters, chemical plants, electric plants and transmission lines, water plants, and wells (which could be contaminated by floodwaters). Critical facilities in the flood zone were identified and listed along with their mailing addresses and phone numbers of contact personnel. 

Due to the preferential extraction of Mo from ocean water, the ocean is the heaviest Mo reservoir of all sources analyzed so far Fig. 2.24, consequently the Mo isotope composition of the ocean is sensitive to redox changes and thus can be nsed as a paleo-redox proxy. 

Fig. 17. Schematic design of a heat flux calorimeter. Both the temperature in the reactor and in the circuit (or jacket) are measured as sensitively and reproducibly as possible. A well-tuned temperature controller keeps the reactor temperature constant by feeding the circuit with warmer or colder water or oil. The circulating water or oil can be taken from either a chilled and a heated reservoir or, as shown, be heated or cooled via external heat exchangers. Calibration is made possible via an electric heater of known power...

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