MXPA97007090A - Determinacion de un parametro de un componente en una composicion - Google Patents

Abstract

A method of determining a parameter selected from the electrical conductivity and the volume fraction of a component in a composition comprising a plurality of components is provided. The method comprises measuring the electrical conductivity of the composition, and selecting a relationship between the conductivity of the composition and a plurality of composition parameters including, for each component, physical parameters representing the conductivity and the volume fraction of the component, said relationship being such that the components are substantially equally represented in said relationship by means of said physical parameters. The selected parameter of the component in the composition is determined fromásaid relationship and the measured conductivity of the composition.

Description

DETERMINATION OF A PARAMETER OF A COMPONENT IN A COMPOSITION FIELD OF THE INVENTION The present invention relates to a method for determining a parameter selected from the electrical conductivity and the volume fraction of a component in a composition comprising a plurality of components. The invention is of particular interest to determine the volume fraction of a component of a ground formation, for example to determine the hydrocarbon content of a hydrocarbon-bearing earth formation. Several known methods for determining such content have been applied so far, these known methods are generally based on empirical models.

-ANTECEDENTS OF THE INVENTION A known method is described in "Electrical conductivities in oil-bearing shaly sands", by Waxman M. H. and Smits L.J.M., SPE paper 1863-A REF: 25639 presented at 42nd Ann, Fall Meeting, Houston, October 1-4, 1967. This publication describes a method for determining a selected parameter from the electrical conductivity and the volume fraction of a component in a composition comprising a plurality of components, wherein the electrical conductivity of the composition is measured, and a ratio between the conductivity of the composition and the conductivity of a component is selected. This known method uses the following relationship, which generally refers to both the axman-Smits model: C0 = Cw / F * + BQV / F * where C0 = conductivity of the rock totally saturated with brine C "= brine conductivity present in the formation F ** = a formation factor B = equivalent conductance of sodium clay exchange cations as a function of Cw Qv = capacity of cation exchange per pore volume of the unit.

The results achieved with this known method are not always sufficiently accurate, probably because of the empirical nature of the Waxman-Smits model which provides a relationship between ground conductivity and several other parameters.

DESCRIPTION OF THE INVENTION It is an object of the invention to provide a more accurate method for determining a parameter selected from the electrical conductivity and the volume fraction of a component in a composition comprising a plurality of components. The method according to the invention for this comprises: measuring the electrical conductivity of the composition; selecting a relationship between the electrical conductivity of the composition and a plurality of parameters of the composition that include, for each component, physical parameters that represent the electrical conductivity and the volume fraction of the component, the components that are substantially represented in the same way the relation by means of the physical parameters; and - determining the parameter selected from the ratio and the measured conductivity of the composition. It should be understood that electrical conductivity is understood as electrical conductivity by itself or any quantitative derivative thereof, such as electrical resistance. In addition, the feature that the components are represented substantially uniformly in the relationship implies that each component is represented in the relationship in substantially the same way as any other component. With the method according to the invention it is achieved that the results of increased accuracy are provided. The selected ratio provides the exact value or result of the individual contributions of the components to the conductivity of the composition. The ratio applied in the method according to the invention is symmetric in the components, that is, the component is not favored over another component. Furthermore, it is found that the method according to the invention provides the desired accuracy by any percolation threshold of the components. In this regard, it is understood that the amount of percolation of a component s.e refers to the degree of continuity of the component in the composition. For example, the percolation of nullification of a component implies that the component is completely dispersed in the composition and the total percolation of a component implies that the component is continuous throughout the entire composition. Advantageously, the plurality of composition parameters includes at least one setting or adjustment parameter, and wherein each setting or adjustment parameter is determined by applying the relation to a set of data obtained by measuring the electrical conductivity of at least one representative sample for said composition. for several magnitudes of at least one of the parameters. Preferably the plurality of parameters includes an auxiliary parameter that depends on the geometric configuration of the components in the composition.

The exact geometric representation by the auxiliary component is achieved if the auxiliary parameter is selected to be a function of a plurality of variables, each variable that depends on the conductivity of one of the components and a mixing coefficient, whereby the coefficients of The mixture depends on the geometric configuration of the components in the composition. Advantageously, the step of determining each setting or adjustment parameter by applying the relation to the data set of the component is carried out through an interative process. Suitably the iterative process includes the application of the relationship repeatedly in a minimization scheme. The minimization scheme is preferably applied to an inconsistency between the measured electrical conductivities of the components and the electrical conductivities of the components that were determined through the relationship. The invention will be described later in greater detail and by means of the following example and the comparative example. Example It is considered an isotropic system with essential spherical inclusions in the form of a ground formation which consists essentially of four components: non-conductive porous rock matrix, non-conductive hydrocarbon fluid, conductive or conductive clay, and conductive brine. The conductivity of the formation depends on the saturation of fractional brine or section of the porous space, and the component of the hydrocarbon fluid is grouped with the matrix of the rock or rocky gangue, both are not conductors. Therefore, the hydrocarbon component and the rocky gangue component only between the equations with the sum of their volume fractions. The effective seff conductivity of this ground formation is evaluated through the expression (sßff - so) + (Lsßff + (l - L) so "1 = S f (sk - s0). (Lsk + (1-L) s0) _1 where so represents the auxiliary parameter in the form of a conductivity tensor k = 1 ... N, N is the number of components sßff represents the conductivity tensor of the sample sjc represents the conductivity tensor of the component k fic represents the volume fraction of the component k L represents the depolarization tensor (shaped tensor) Preferably the depolarization tensor is positive and has unit trace. In an attractive modality, the depolarization tensor equals 1/3 of the unit's tensioner. The term sso denotes an auxiliary parameter which can be considered to be an additional housing means in which the components are aggregated until the host means or host means has been completely replaced by the components so that the fraction is associated of volume with the host medium or host medium.

The existence of the host means allows the model to be symmetric in all its constituents: none of the rock, clay or brine components in the model is favored over any of the other components. The dependence of s0 on several parameters, although not determined, controls or governs the operation of the percolation of the model. The adjustment s = ssaiuera leads to the Approximation of the matrix T Average known, also referred to as the generalized Clausius-Mossotti equation. This model has a clear asymmetry between the brine component and the other components since only the brine component will percolate, irrespective of its volume fraction. Selecting a conductivity of the self-consistent host environment, so = seff, leads to the known Coherent Potential Approximation, also referred to as the Bruggeman generalized equation. This model is symmetric in all the components but has the disadvantage of requiring high percolation thresholds, not real high for each component. In a suitable embodiment, the auxiliary parameter s0 is selected as follows: so = S hk sk; for k = 1, 2, 3 where hk represents the coefficient tensor of the mixture belonging to the component k, said tensor contains mixing coefficients that represent geometric information in the spatial distribution of the components in the formation. These coefficients determine the connectivity, that is, the amount of percolation of the individual components. The coefficients are not negative and meet the normalization condition:? hk = 1; for k = 1, 2, 3 The normalization performance ensures that the resulting effective conductivity seff satisfies the Hashin-Shtrikman bonds, which are well known to those skilled in the art. In addition, a component with a smaller fade or void volume fraction can not be percolated, since the corresponding connectivity parameter must fade or be nullified: lim hk = 0; for fk = - > 0 Properly the tensor of the mixing coefficient is selected to be hk =? fcfkVk (?? nfnvn) -l where k, n = 1 ... N, N is the number of components in the plurality of components? k represents the percolation velocity tensor that belongs to the component k fk represents the volume fraction of the component kv represents the exponent of percolation belonging to the component k Conveniently at least one of hk,? kyv forms a suitable or adjustment parameter. A data set in 27 samples of the slate sand core have been used to test the invention, this data set is described in the SPE paper indicated above. This publication provides C0 - Cw curves in the core samples that vary from almost clean sand (Qv = 0.017 ec / 1) to extremely slender sand (Qv = 1.47 ec / 1). The samples contain Kaolinite, Montmorillonite and Hita, either in combination or separately in each sample. The characteristic petrophysical data of each sample is listed in the attached table, in which f denotes the porosity of the sample, k denotes the permeability of the sample, and Qv means the cation exchange capacity per volume of the unit's pore. The conductivity of each sample in the fully brine saturated condition was measured by eight to ten salinities of the brine, In addition, the measurements of the concentration potential of the membrane were made from the samples. They were selected as follows: 1) Brine The fraction of the brine volume, fb, is determined by the porosity, the amount of water combined with clay, and the saturation of the water S "The brine conductivity f (= CW) is determined by brine salinity and brine temperature The two parameters of percolation,? byv, are free parameters 2) Rock / Hydrocarbon The volume of hydrocarbons, fhcr is determined by the porosity totality, the amount of water combined with clay, and the saturation of hydrocarbons 1-SW, while the volume of the rock matrix, fr, is calculated using the rule of sum and volume fractions. Both the rock and the hydrocarbon have lost conductivity or conductivity that tends to zero. The percolation parameters? R and? C of both components were adjusted to the value 1. The coefficient of the mixture pertaining to rock / hydrocarbon hr / C followed by the condition? hk = 1. 3) Clay; The volume of clay fc and the conductivity of clay sc are parameters of free fixation or adjustment. The percolation rate? C was set to a value of 0, which is a suitable choice for non-laminated clays. Furthermore, it seems that an additional free parameter does not provide a significant improvement in the adaptation of the model to the data set. The C0 - Cw measurements were made for a range of extreme salinity, mainly a salinity of brine between 1 - 300 g / 1. For a given sample the volume fraction of brine varied only slightly over the full salinity range. In view of this the percolation parameter v was adjusted equal to the unit of the test, whereby it reduces the percolation parameter hb to a constant, and reduces the number of free parameters to three. For each sample, an adjustment to the curve of C0 - C "was made by minimizing the relative inconsistency defined as: where C0, caic = the calculated conductivity of the rock samples completely saturated with brine; Co, measured = the measured conductivity of the rock samples saturated with brine; ? = sum or total on the salinities. The results for the three fixation or adjustment parameters fc, sc and hb, and the relative inconsistency are given in the appended Table. In addition, the Table provides the incoherence between the membrane potential (? Caic) determined by the method of the invention and the measured membrane potential (? Mido): The membrane potential is a particularly interesting amount to be a non-destructive, direct measure of the contribution of clay to total conductivity, which has not been used to determine the parameters of fixation or adjustment.

To illustrate the invention more specifically, reference is made to the following comparative example. Comparative Example As described in Ref. 1 above, far from the data set in the 27 core samples, in addition to an empirical model which is generally referred to as the Waxman-Smits model. To compare the method according to the invention with the Waxman-Smits model, the relative incoherence between the measured conductivities and the conductivities found from the Waxman-Smits model, and the relative incoherence between the concentration membrane potentials measured, were determined. and the concentration membrane potentials found from the Waxman-Smits model. These relative inconsistencies for all 27 samples are listed in the Table. In the application the Waxman-Smits model, used, has been made from the well-known expression. with F * = f "m where m is a free parameter (also referred to as the cementing exponent), Qv is determined from the sample measurements, until the porosity f, and standard hydrographic chart B has been determined. used to calculate the salinity and temperature effects in the conductivity measurements From a comparison between the incoherence values found using the method according to the invention, and the inconsistency values found using the Waxman-Smits model, it is of course that the method according to the invention provides improved results, especially the extremely low incoherence values for the concentration membrane potential, such values are also fairly constant over the complete Qv range, indicate that the method according to the invention provides results of increased accuracy The method according to the invention can be suitably applied to determine the a volume fraction of brine or hydrocarbon in a ground formation, whereby a well diagram is provided which "represents the electrical conductivity of the formation. Such an application may, for example, be carried out in the following manner. The wellbore diagram of the electrical conductivity of the earth formation is made using a tool of longitudinal profile lowered in a borehole formed in the earth formation. For an isotropic formation with brine components (subscript B), clay (subscript C), and non-conductive rock + hydrocarbon (R / HC subscript) the rock and the hydrocarbon are grouped together because of their conductivities canceled or vanished. The selected relationship then is: sßff + 2 s0 k = l sk + 2sQ where so = S hs hk =? kfkVk (?? nfnVn) "1 in which s0 represents the auxiliary parameter k, n = l ... N, N is the number of components seff represents the conductivity of the ground formation sk represents the conductivity of the component k fk represents the volume fraction of the component k hk represents the mixing coefficient belonging to component k; ? k represents the percolation coefficient that belongs to the component k vk, n represents the percolation exponent belonging to the component k, n. Each component k has four parameters: fk, k,? K, and vk, of which fB, sB and sR / Hc are measured directly. Also,? C = 0 for scattered clay. From the addition rules hR / Hc and FR / HC followed, the parameters which are still to be determined are sc,? B, vB and fc. These parameters are determined through the posterior model in experimental data. sc,? B and vB are invariable over the geological formation, while fB will be deeply dependent. The experimental data for the determination of the parameter consist of measurements of the well diagram of a zone containing brine, measurements of the Laboratory Resistance Factor of Formation (FRF) and saturation experiments with brine. The chart information from the brine-containing zone is used to correlate the local parameter fc for combinations of suitable diagrams / diagrams, as is known to those skilled in the well-logging art. sc,? B and FB and the correlation of fc for combinations of suitable diagrams / diagrams can be used in bearing or hydrocarbon bearing formations. From the well diagram, the above relationship and the indicated parameters, the volume fraction of brine and therefore also the volume fraction of the hydrocarbon is determined as a function of depth.

(Jatos petrophysical parameters inconsistency incoherence for the present invention for the previous technical sample FK. [MD] Qr? C ° c S? 0c.? AS?, -c.? 1, No. eec / 1] [mS / cm ] 1 0.239 659 0.017 0.0532 2.9581 0.2016 0.002 0.018 0.009 0.026 2 0.212 105 0.052 0.1822 1.3537 0.2038 0.002 0.035 0.061 0.099 3 0.231 397 0.052 0.1376 1.8607 0.2517 0.002 0.014 0.031 0.097 4. 0.080 1.34 0.26 0.1323 1.3325 0.1788 0.010 0.119 0.045 0.010 5 0.154 55 0.2 0.3216 1.4851 0.3752 0.005 0.042 0.149 0.128 6 0.215 29 0.095 0.3467 1.0193 0.1370 0.003 6.026 0.206 0.257 S o 7 0.171 3.5 0.053 0.3779 0.7847 0.1200 0.008 0.016 0.312 0.446 8 0.171 7.66 0.053 0.3119 0.8994 0.1274 0.007 0.018 0.234 0.366 9 0.199 57 0.085 0.3935 1.0627 0.1613 0.007 0.025 0.276 0.351 10 0.125 0.042 0.253 0.432 0.3113 0.0255 0.029 0.074 0.483 0.262 11 0.125 0.0106 0.253 0.4007 0.2590 0.0233 0.037 0.057 0.348 0.203 12 0.110 1.86 0.28 0.5855 0.8601 0.1326 0.018 0.010 0.760 0.542 13 0.110 0.3 0.28 0.5998 1.0802 0.1286 0.020 0.016 0.868 0.589 14 0.110 2.08 0.28 0.5815 1.4104 0.1998 0.054 0.029 0.854 0.539 15 0.092 0.128 0.41 0.509 0.6025 0.0402 0.027 0.025 0.917 0.449 16 0.103 0.024 0.67 0.7202 1.4537 0.1103 0.010 0.013 1.263 0.529 17 0.140 0.575 0.33 0.7763 1.5783 0.0977 0.050 0.013 1.606 0.919 18 0.259 3.78 0.59 0.7033 2.8964 0.1357 0.012 0.007 1.173 0.507 ' petrophysical data parameters inconsistency incoherence for the present technique prior invention shows F A: [mDJ Qv < Pc sc S.-C S? V S -C S? No. tec / 1] [mS / cml 20 0.259 44.8 0.59 0.5978 3.4771 0.2113 0.003 0.023 0.674 0.286 21 0.238 315 0.29 0.6984 1.3859 0.1812 0.009 0.031 0.632 0.546 22 0.225 1.92 0.72 0.7651 2.4172 0.0766 0.016 0.013 1.808 0.637 23 0.242 54.3 1.04 0.7306 4.0758 0.1165 0.022 0.011 1.640 0.490 24 0.216 0.546 0.81 0.7751 2.6418 0.0659 0.021 0.014 2.103 0.703 NJ 0.187 0.0348 1.27 0.7995 3.4510 0.0726 0.005 0.040 0.490 0.369 26 0.229 1.53 1.47 0.7491 5.0425 0.0887 0.042 0.026 2.155 0.470 27 0.209 0.263 1.48 0.7656 5.1455 0.08841 0.001 0.067 | 0.495 0.326 1 TABLE It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property

Claims (22)

1. A method for determining a parameter selected from the electrical conductivity and the volume fraction of a component in a composition comprising a plurality of components, the method is characterized in that it comprises: measuring the electrical conductivity of the composition; - selecting a relation between the electrical conductivity of the composition and a plurality of parameters of the composition that include, for each component, physical parameters that represent the electrical conductivity and the volume fraction of the component, the components are represented substantially equal in the ratio by means of physical parameters; and determining the parameter of selection of the ratio and the measured conductivity of the composition.

2. "" The method according to claim 1, characterized in that the plurality of parameters of the composition include at least one parameter of fixation or adjustment, and where each parameter of fixation or adjustment is determined by applying the ratio of a set of data obtained by measuring the electrical conductivity of at least one representative sample of the composition for various magnitudes of at least one of the parameters.

3. The method according to claim 1 or 2, characterized in that the plurality of parameters includes an auxiliary parameter that depends on the geometric configuration of the components in the composition.

4. The method according to claim 3, characterized in that the relation is selected to be (< feíí-s0). (Lseff + (lL) so) "1 =? Sk (sk - s0). (Lsk + (lL) so)" 1 where s0 represents the auxiliary parameter in the form of a conductivity tensor k = 1 ... N, N is the number of components sßff represents the conductivity tensor of the sample sk represents the conductivity tensor of the component kf represents the volume fraction of the component k L represents a depolarization tensor.

5. The method according to claim 3 or 4, characterized in that the auxiliary parameter is selected to be a function of a plurality of variables, each variable that depends on the conductivity of one of the components and a mixing coefficient, so that the coefficients of the mixture depend on the geometric configuration of the components in the composition.

6. The method according to any of claims 3-5, characterized in that the auxiliary parameter is selected to be s0 = S hksk where so represents the auxiliary parameter in the form of a representative conductivity tensor for the conductivity in the three principal directions; k = 1 ... N, N is the number of components; sk represents the conductivity tensor of component k; hk represents the coefficient tensor of the mixture that belongs to the component k.

7. The method according to claim 5 or 6, characterized in that the coefficients of the mixture are selected such that the sum of the coefficients of the mixture substantially equals the unit.

8. The method according to any of claims 5-7, characterized in that the coefficients of the mixture are not negative.

9. The method according to any of claims 5-8, characterized in that each mixing coefficient is selected to be a function of at least the volume fraction of the component belonging to the mixture coefficient.

10. The method according to claim 9, characterized in that the function is a monotonic increase function in the volume fraction of the component belonging to the mixture coefficient- '.

11. The method according to claim 9 or 10, characterized in that the function is selected so that the coefficient of the mixture is canceled to cancel the volume fraction of the component belonging to the mixture coefficient.

12. The method according to any of claims 5-11, characterized in that each mixing coefficient is selected as hk (?? nfnVn) 1 where k, n = 1 ... N, N is the number of components in the plurality of components? k represents a percolation velocity tensor belonging to the component k fk represents the volume fraction of the component k vk, n represents a percolation exponent belonging to the component k, n.

13. The method according to claim 12, characterized in that at least one of hk,? Ic and v form a setting or adjustment parameter.

14. The method according to any of claims 4-13, characterized in that the depolarization tensor is positive.

15. The method according to any of claims 4-14, characterized in that the depolarization tensor has a unit trace.

16. The method according to any of claims 4-15, characterized in that the depolarization tensor equals 1/3 of the unit's tensioner.

17. The method according to any of claims 1-16, characterized in that the step for determining each setting or adjustment parameter by applying the relation of the data set is carried out through an iterative process.

18. The method according to claim 17, characterized in that the iterative process includes repeatedly applying the relationship in a minimization scheme.

19. • The method according to claim 18, characterized in that the minimization scheme is applied to a mismatch or imbalance between the measured electrical conductivities of the components and the electrical conductivities of the components as determined through said relationship.

20. The method according to any of claims 1-19, characterized in that the composition includes a ground formation.

21. The method according to claim 20, characterized in that the earth formation includes at least one rock, brine, hydrocarbon fluid and clay.

22. The method according to claim 21, characterized in that the parameter which is determined forms the volume fraction of one of the hydrocarbon fluid and the brine.