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The formation resistivity factor has been the subject of much laboratory investigation. The terms of this relationship have been subjected to even more speculation. The porosity exponent, used in the petroleum industry, has been known by a number of different names, of which only one of those names, shape factor2, adequately describes the attribute of the rock or pore volume which influences the value of the exponent. Both Archie's formation resistivity factor and the modified formation resistivity factor are shown below.
- Geology > Mineral (0.72)
- Geology > Rock Type > Sedimentary Rock (0.69)
Resistivity well-logging devices respond to all of the electrically conductive matter found within their respective ranges of investigation. To be consistent with this concept in shaly sand interpretation, the user must have some means to estimate the total rock porosity containing electrically conductive interstitial solutions and a means to estimate the contribution of each solution to the total conductivity. It will be one of the purposes of this paper to show the user a method for ascertaining usable values of these important parameters for use in Archie's basic water saturation relationship. A method for the evaluation of effective porosity from neutron and density well-logging responses has been developed by others, and is well documented in literature. A method for the evaluation of total porosity, as defined herein, has not been described in literature. In this paper, the neutron and density well-logging responses will be used to estimate the volumes of both effective and total porosities. Before these volumes can be determined to any degree of reliability in heterogeneous shaly sands, the influences of constituents other than quartz and water must be recognized and nullified. These constituents may be clay, cement or fragments of material other than quartz or clay, or hydrocarbon fluids which have densities different from that of interstitial water. In the process of evaluating effective and total porosities, other distinguishing features about the reservoir rock may be recognized. This additional information will help the user to understand the producibility of the reservoir rock of interest.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (1.00)
- Geology > Mineral > Silicate (1.00)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
The primary purpose of this report is to propose a generalized theory pertaining to resistivity well log evaluation of reservoir beds. The notable difference between the concept proposed in this paper and the Archie method is: Archie and others considered formation resistivity to be a function of porosity, a rock-related parameter, and of water saturation, a porosity considers resistivity to be a function of the bulk volume and geometry of formation water. parameter, whereas the technique proposed herein A new formation resistivity factor relationship is proposed. This relationship is based on an "apparent formation resistivity factor," which is considered to be the general factor relating the existing resistivity of a unit volume of reservoir rock to the quantity of electrically effective formation water present in the rock. The apparent formation resistivity factor, therefore, is defined as Fa which is equal to. The proposed apparent formation resistivity factor-porosity relationship is at water saturations less than or equal to 100%. The b term is a secondary conductivity coefficient described in detail in this paper. The exponent m" is related to both the porosity exponent, m, and the saturation exponent, n. Archie's relationship, where is a special case of the proposed apparent formation resistivity factor, Fa. The physical significance of such terms as the secondary conductivity coefficient, b, the porosity exponent, m, and the saturation exponent, n, will be shown in the course of explanation of the proposed theory. It will also be shown that in the modified formation resistivity factor-porosity relationship, where the a coefficient has no significance directly relatable to a property of rock or water.
- North America > United States > Texas (1.00)
- North America > Canada (1.00)
- Europe (1.00)
- North America > United States > Oklahoma (0.68)
- Geology > Mineral (1.00)
- Geology > Sedimentary Geology (0.67)
- Geology > Geological Subdiscipline (0.67)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.46)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.46)
- North America > United States > South Dakota > Williston Basin (0.99)
- North America > United States > North Dakota > Williston Basin (0.99)
- North America > United States > Montana > Williston Basin (0.99)
- North America > United States > Louisiana > Bowie Field (0.99)