# F can often be extracted from this new measured porosity of your development through the dating

F can often be extracted from this new measured porosity of your development through the dating

Well logs render understanding of the latest formations and standards on subsurface, aligned mostly during the identification and you will testing from perhaps active horizons.

## Dedication from saturation

Liquid saturation ’s the fraction of pore level of the tank material that’s full of drinking water. It’s basically presumed, unless if not understood, that the pore frequency perhaps not filled up with water is filled with hydrocarbons. Choosing liquid and you can hydrocarbon saturation is among the basic objectives regarding well signing.

## Brush formations

All-water saturation determinations regarding resistivity logs from inside the clean (nonshaly) structures with homogeneous intergranular porosity are based on Archie’s liquids saturation formula, otherwise differences thereof. [1] [2] The fresh equation are

For ease, brand new saturation exponent letter is often drawn since the dos. Laboratory tests have shown that try https://datingranking.net/local-hookup/bunbury/ a good worthy of for mediocre circumstances. For lots more exacting performs, electric proportions on the cores often produce top quantity to have letter, a great, and you may m. When key measured opinions was not available, the values off a good and you can meters inside Eq. 4 shall be projected the following: when you look at the carbonates, F=1/? dos is oftentimes utilized; for the sands, F=0.62/? dos [3] (Simple formula), otherwise F=0.81/? 2 (a less strenuous function about equivalent to brand new Humble formula). These types of equations are often developed on the spreadsheets and they are obtainable in most record translation application.

The accuracy of the Archie equation, Eq. 1 and its derivatives, depends in large measure, of course, on the accuracy of the fundamental input parameters: Rw, F, and Rt. The deep resistivity measurement (induction or laterolog) must be corrected, therefore, for borehole, bed thickness, and invasion (see the page Formation resistivity determination for more details). It is almost never safe to make the assumption „deep = Rt.“ The most appropriate porosity log (sonic, neutron, density, magnetic resonance, or other) or combination of porosity and lithology measurements must be used to obtain porosity, and the proper porosity-to-formation factor relationship must be used. Finally, the Rw value should be verified in as many ways as possible: calculation from the SP curve, water catalog, calculation from nearby water-bearing formation, and/or water sample measurement.

Approach strategies for choosing liquid saturation include analysis out of cores cut that have lowest-invasion oils-oriented muds (OBMs) and you will solitary really chemical substances tracer (SWCT) assessment. These independent methods are often used to calibrate journal analyses.

## Resistivity compared to. porosity crossplots

Eq. 7 shows that for Rw constant, ?Sw is proportional to is the quantity of water per unit volume of formation. To emphasize the proportionality between ? and , Eq. 7 may be rewritten:

For a 100% water-saturated formation, Sw = 1 and Rt = R0. If R0 for water-saturated formations is plotted on an inverse square-root scale vs. ?, all points should fall on a straight line given by .

Furthermore, the points corresponding to any other constant value of Sw will also fall on a straight line, because in Eq. 7 the coefficient is constant for constant values of Rw and Sw.

Fig. 1 shows several points plotted over an interval in which formation-water resistivity is constant (as indicated by constant SP deflections opposite the thick, clean permeable beds). Assuming that at least some of the points are from 100% water-bearing formations, the line for Sw = 1 is drawn from the pivot point (? = 0, Rt = ?) through the most northwesterly plotted points. The slope of this line defines the value of Rw as shown on Fig. 1, for ? = 10%, R0 = 6.5 ohm•m. For this formation, the most appropriate F – ? relation is F = 1/? 2 . Thus, for ? = 10%, F = 100. Because Rw = R0/F, Rw = 0.065 ohm•m, as shown.