Patent US3379995A successfully refreshed from Google Patents.
EP0351902A1
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EP
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Method of determining the porosity of an underground formation being drilled
Assignee: Anadrill International SA
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Filing: 1989-06-27
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Granted: —
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Expires: 2009-06-27
Abstract
Abstract The invention relates to a method of determining the porosity of an underground formation being drilled by a rotating drill bit mounted at the lower end of a drill string. The torque (TOR) and the weight (WOB) applied on the bit when drilling the underground formation are measured; the effect of the geometry of the drill bit on the torque and weight on bit response is determined; the porosity (phi) of the formation being drilled is derived from the measured TOR and WOB taking into account the effect of the geometry of the drill bit. Preferentially, the porosity phi is determined from the following equation: TOR = (k₁ + k₂.phi) WOBª where k₁, k₂ and a are parameters characteristic of the geometry of the drill bit.
Inventors
- 👤 David Curry
- 👤 Michael Sheppard
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 11:31
CPC Classifications
E; E21; E21B; E21B44/00; E21B49/00; E21B49/003
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
90 words
Method of determining the porosity of an underground formation being drilled by a rotating drill bit mounted at the lower end of a drill string, comprising the steps of measuring the torque (TOR) and the weight (WOB) applied on the bit when drilling the underground formation; determining the effect of the geometry of the drill bit on the torque and weight-on-bit response; and determining the porosity (phi) of the formation being drilled from the measured TOR and WOB, taking into account the effect of the geometry of the drill bit.
Claim 2
Dependent Claim
90 words
Method of determining the porosity of an underground formation being drilled by a rotating drill bit mounted at the lower end of a drill string, comprising the steps of measuring the torque (TOR) and the weight (WOB) applied on the bit when drilling the underground formation; determining the effect of the geometry of the drill bit on the torque and weight-on-bit response; and determining the porosity (phi) of the formation being drilled from the measured TOR and WOB, taking into account the effect of the geometry of the drill bit.
Claim 3
Dependent Claim
89 words
Method according to claim 1, wherein said step of determining the effect of the geometry of the drill bit comprises drilling with said bit, or a bit of substantially identical geometry, in the field or in the laboratory, formations of different known porosities; measuring successive values of the torque and weight applied on the bit while drilling and correlating said successive values and the known porosities to establish an experimental cross plot of TOR as a function of WOB and porosity corresponding to the geometry of the drill bit.
Claim 4
Dependent Claim
56 words
Method according to claim 2, wherein the porosity of the formation being drilled in the field by said drill bit is determined by measuring at least one value of TOR and WOB and by using the experimental cross plot corresponding to the geometry of said drill bit to determine the porosity of the formation being drilled.
Claim 5
Dependent Claim
50 words
Method according to claim 1, wherein said step of determining the effect of the geometry of the drill bit comprises the mathematical modelling of the drill bit so as to produce a model describing the effect on the torque and weight on bit response for different geometries of drill bits.
Claim 6
Dependent Claim
46 words
Method according to one of the preceding claims, wherein the step of determining the porosity (phi) is carried out in accordance with the following equation: TOR = (k₁ + k₂.phi) WOBª where k₁, k₂ and a are parameters characteristic of the geometry of the drill bit.
Claim 7
Dependent Claim
58 words
Method according to claim 5, wherein the value of the parameter a is determined, for a geometry of drill bit, by measuring successive values of TOR and WOB while drilling with said geometry of drill bit in a formation of substantially constant porosity and by correlating the measured values of TOR and WOB to determine the parameter a.
Claim 8
Dependent Claim
24 words
Method according to claim 6 or 7, wherein the value of parameter a is chosen between 0.5 and 2, preferably between 1 and 1.5.
Claim 9
Dependent Claim
17 words
Method according to claim 7, wherein the value of parameter a is chosen equal to about 1.2.
Claim 10
Dependent Claim
75 words
Method according to one of the claims 5 to 8, wherein the values of parameters k₁ and k₂ are determined for a geometry of drill bit by drilling, in the field or in the laboratory formation of at least two known different porosities with a drill bit having said geometry, measuring the values of TOR corresponding to at least one value of WOB and by computing k₁ and k₂ from the equation of claim 5.
Claim 11
Dependent Claim
51 words
Method according to one of the preceding claims, wherein the change in the states of wear (T) of the drill bit is monitored whilst drilling and the effect of the geometry of the drill bit is adjusted to account for the change in the state of wear of the drill bit.
Claim 12
Dependent Claim
87 words
Method according to claims 5 and 10, wherein the values of the parameters k₁ and k₂ are computed as a function of the state of wear (T) of the drill bit by measuring the successive values of TOR and WOB whilst drilling formationhs of at least two known porosity values (phi), monitoring the state of wear T of the drill bit while drilling and computing the different values of k₁ and k₂ as a function of T by correlating the values of TOR, WOB, phi and T.
References Cited (Backward Citations)
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