Fractures carbonates

Shallow water carbonate (reefs carbonate muds) Reservoir quality governed by diagenetic processes and structural history (fracturing). Prolific production from karstified carbonates. High and early water production possible. Dual porosity systems in fractured carbonates. Dolomites may produce H S. 

Field analogues should be based on reservoir rock type (e.g. tight sandstone, fractured carbonate), fluid type, and environment of deposition. This technique should not be overlooked, especially where little information is available, such as at the exploration stage. Summary charts such as the one shown in Figure 8.19 may be used in conjunction with estimates of macroscopic sweep efficiency (which will depend upon well density and positioning, reservoir homogeneity, offtake rate and fluid type) and microscopic displacement efficiency (which may be estimated if core measurements of residual oil saturation are available). 

The overall reaction in the replacement of hydrogen is exothermic enough (AG298 = -103.4 kcal mole 1) to fracture carbon--carbon bonds if it were to occur by a concerted mechanism or if it were to occur on several adjacent carbon atoms simultaneously. The comparison of 86 versus 103 kcal mole-1 has been cited in many previous discussions as an obvious basis for the prediction of the failure of direct fluorination methods. For the rapid reaction rates employed in most previous experiments, this is a valid argument. 

Figure 1. SEM image of a fractured carbon film (upper part smooth surface, middle fracture, bottom support).

Adibhatla, B., Mohanty, K.K., 2008. Oil recovery from fractured carbonates by surfactant-aided gravity drainage laboratory experiments and mechanistic simulations. SPE Reservoir Engineering and Evaluation (SPEREE) (February), 119—130. 

Microfibrils are also present, with dimensions between a BSU and the texture of fractured carbon fibers observed in micrographs. It is probable that the fine structure within the micofibril controls the compressive strength failure mechanisms. 

If subjected to overload, carbon resistors usually decrease in resistance since carbon has a negative temperature coefficient. This causes more current to flow through the resistor, so that the temperature rises and failure occurs, usually by fracturing. Carbon resistors have a power rating between 0.1 and 2W, which should not be exceeded. 

A predominantly naturally fractured carbonate formation, potentially leading to propped-fracture compHcations... 

In naturally fractured carbonates, propped fracturing may not be appropriate because of the difficulty in placing necessary amounts of proppant. The tortuous paths often present and complex stress properties can result in fracture geometry that is convoluted that it becomes impossible to maintain proppant injection. 

Grove, D.B. and W.A. Beetem. 1971. Porosity and dispersion constant calculations for a fractured carbonated aquifer using the two well tracer test method. Water Resources Research 7(1) 128-134. 

Iwere, F.O., Moreno, J.E., Apaydin, O.G., 2002. Vug characterization and pore volume compressibility for numerical simulation of vuggy and fractured carbonate reservoirs. SPE 74341, In SPE Intemat. Petroleum Conf. Exhib., Mexico. 

Rasmus, J.C., 1983. A variable cementation exponent, m, for fractured carbonates. Log Anal. 

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