Method and apparatus for characterizing earth formation properties through joint pressure-resistivity inversion
First Claim
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1. A method for determining values for at least one parameter of a formation traversed by a borehole at a plurality of locations along the borehole, said at least one parameter including at least one of permeability, factors of relative permeability, and skin factors, including:
- a) estimating values for a plurality of formation parameters for said plurality of formation locations;
b) using the estimated values for said plurality of formation locations as inputs to a formation pressure transient model, and as inputs to a formation saturation-conductivity model, said formation pressure transient model providing computed pressures as outputs and said formation saturation-conductivity model providing computed conductivity profiles as outputs, and a first of said formation pressure transient model and said formation saturation-conductivity model providing an additional output which is used as an additional input to a second of said formation pressure transient model and said formation saturation-conductivity model;
c) injecting fluid into the borehole;
d) using a borehole tool, measuring indications of pressures and measuring indications of conductivities of different locations in said formation as fluid moves from the borehole into the formation;
e) iteratively comparing said indications of measured pressures and indications of measured conductivities with indications of said computed pressures and indications of said computed conductivity profiles and providing feedback values to change said estimated values in order to provide a determination of said at least one parameter at said at least plurality of locations.
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Abstract
Methods and apparatus for estimating values for formation parameters such as permeability, relative permeability, and skin factors for a plurality of locations in the formation are provided. Fluid is forced into a capped borehole at a measured rate, and a borehole logging tool is run in the borehole to measure indications of pressure and conductivity. Estimates of the parameters and the measured fluid flow rate(s) into the formation are used in conjunction with a jointly inverted pressure transient model and saturation-conductivity model in order to compute indications of expected pressure and indications of expected conductivity-related profiles as a function of depth and time. The expected pressures and expected conductivity related profile indications are then compared to the pressures and conductivity indications measured by the borehole logging tool, and an iterated comparison between the computed values and the measured values is used to provide determinations of the formation parameters. According to a preferred embodiment, the pressure transient model is for compressible flow and provides an estimated calculated fluid flow into the layers of the formation; the estimated calculated fluid flow being an input to the saturation-conductivity model which is for incompressible flow.
78 Citations
25 Claims
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1. A method for determining values for at least one parameter of a formation traversed by a borehole at a plurality of locations along the borehole, said at least one parameter including at least one of permeability, factors of relative permeability, and skin factors, including:
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a) estimating values for a plurality of formation parameters for said plurality of formation locations; b) using the estimated values for said plurality of formation locations as inputs to a formation pressure transient model, and as inputs to a formation saturation-conductivity model, said formation pressure transient model providing computed pressures as outputs and said formation saturation-conductivity model providing computed conductivity profiles as outputs, and a first of said formation pressure transient model and said formation saturation-conductivity model providing an additional output which is used as an additional input to a second of said formation pressure transient model and said formation saturation-conductivity model; c) injecting fluid into the borehole; d) using a borehole tool, measuring indications of pressures and measuring indications of conductivities of different locations in said formation as fluid moves from the borehole into the formation; e) iteratively comparing said indications of measured pressures and indications of measured conductivities with indications of said computed pressures and indications of said computed conductivity profiles and providing feedback values to change said estimated values in order to provide a determination of said at least one parameter at said at least plurality of locations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A system for determining values for at least one parameter of a formation traversed by a borehole at a plurality of locations along the borehole, said at least one parameter including at least one of permeability, factors of relative permeability, and skin factors, said system comprising:
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a) means for injecting fluid under pressure into the borehole; b) means for measuring a flow rate at which said fluid is injected into the borehole; c) a borehole tool means for traversing the borehole, including a plurality of electrode means for generating electrical signals and for measuring resulting electrical signals while said injected fluid is moving into the formation, and pressure measurement means for measuring pressures in the borehole while said injected fluid is moving into the formation; and d) processing means coupled to the borehole tool said processing means for (i) receiving indications of said measured resulting electrical signals and indications of said measured pressures, (ii) storing estimated values for a plurality of formation parameters for said plurality of formation locations, (iii) storing a formation pressure transient model and a formation saturation-conductivity model, and (iv) processing said indications of said measured resulting electrical signals and said indications of said measured pressures by using said estimated values for said plurality of formation locations and said measured flow rate as inputs to a formation pressure transient model and as inputs to a formation saturation-conductivity model, said formation pressure transient model providing computed pressures as outputs and said formation saturation-conductivity model providing computed conductivity profiles as outputs, and a first of said formation pressure transient model and said formation saturation-conductivity model providing an additional output which is used as an additional input to a second of said formation pressure transient model and said formation saturation-conductivity model, and by iteratively comparing said indications of measured pressures and indications of measured electrical signals with indications of said computed pressures and indications of said computed conductivity profiles and providing feedback values to change said estimated values in order to provide a determination of said at least one parameter at said plurality of locations. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification
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Current AssigneeSchlumberger Technology Corporation (Schlumberger NV)
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Original AssigneeSchlumberger Technology Corporation (Schlumberger NV)
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InventorsKuchuk, Fikri John, Belani, Ashok, Ayestaran, Luis, Ramakrishnan, Terizhandur S., Habashy, Tarek M.
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Primary Examiner(s)McElheny, Jr., Donald E.
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Application NumberUS08/843,206Time in Patent Office1,121 DaysField of Search702/12, 702/13, 73/152.31, 73/152.41, 73/152.52US Class Current702/12CPC Class CodesE21B 49/008 by injection test; by analy...
