Invasion depth

Two important parameters are usually needed by production engineers dealing with water injection or disposal wells. These parameters are (1) well injectivity and (2) invasion depth. 

Where D is the invasion depth and 0m is the porosity of porous medium. 

Eylander used core flood tests to predict filter cake properties. Equations 23 and 24 can be used to determine the injections well s half time (a = 0.5). Eylander, however, suggested further research is needed to better determine the invasion depth, D. 

While we have demonstrated how quantities of interest, such as permeability, porosity, hydrocarbon viscosity, and pore pressure, can be uniquely obtained, at least from invasion depth data satisfying our equations for piston-like fluid displacement, the actual problem is far from solved even for the simple fluid dynamics model considered here. For one, the tacit assumption that invasion depths can be accurately inferred from resistivity readings is not entirely correct invasion radii are presently extrapolated from resistivity charts that usually assume concentric layered resistivities, which are at best simplified approximations. And second, since tool response and data interpretation introduce additional uncertainties, not to mention unknown three-dimensional geological effects in the wellbore, time lapse analysis is likely to remain an iterative, subjective, and qualitative process in the near future. With these disclaimers said and done, we now demonstrate via numerical examples how formation parameters might be determined from front radii in actual field runs. 

Mud filtrate invasion is normally restricted to within a few inches into the formation, after which the build up of mudcake prevents further filtrate loss. If resistivity tools with different depths of investigation (in the invaded and non-invaded zones) are used to... 

Seismic studies are very useful when information is lacking on subsurface stratigraphy, or when the depth to bedrock, the water table, a particular bed or formation, or some other layer in the subsurface must be determined without drilling. Seismic lines can be set up to produce stratigraphic cross sections and they can be a very useful "non-invasive" inves-... 

Most recently Puppels and co-workers to determine the concentration of defined NMF component non-invasively in vivo in the SC have pioneered the use of confocal Raman microscopy.84 Figure 18.3 shows depth profiles for the major filaggrin derived components, urea and lactate obtained using this technique. Evidence of leaching from the skin surface is characteristically seen in most profiles and the precipitous drop off in levels of filaggrin derived components deeper in the SC indicates the boundary at which filaggrin hydrolysis is rapidly initiated. 

Figure 9 Measurements of " C/C ratio in a benthic coral from 1.8 km depth in the northern Atlantic reveal that the base has an apparent age 650 radiocarbon years younger than the top. Yet °Th ages on the base and crest are nearly identical (1.54XlO" yr calendar years). Adkins et al. (1998) (reproduced by permission of Jess Adkins) attribute this difference to an abrupt invasion of low " C and high cadmium content Southern Ocean water.

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