# US 10,370,955 B2 · Method of calculating pore pressure while drilling > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,370,955 B2 - Document ID: US10370955B2 - Status: Granted - Kind: B2 - Application number: 14/645,535 - Filed: 2015-03-12 - Published: 2016-09-15 - Granted: 2019-08-06 - Earliest claimed: 2015-03-12 - Assignees: Statoil Gulf Services LLC - Applicants: Statoil Gulf Services LLC - Inventors: Giuseppe De Prisco - Web page: https://patentgrep.com/patent/US10370955B2 ## CPC - E21B 49/003: {by analysing drilling variables or conditions (E21B49/005 takes precedence; systems specially adapted for monitoring a plurality of drilling variables or conditions E21B44/00)} - G01V 3/38: Processing data, e.g. for analysis, for interpretation, for correction - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract A method for calculating pore pressure of a subsurface includes the steps of obtaining a resistivity value while drilling in a region wherein there is a shallow depth (reference depth) where shale is in a hydrostatic condition, or where shale is not in hydrostatic condition but where the pore pressure at such depth can be estimated and calculating, using a processor, a pore pressure at a drilling location based on the following Formula (I): PP=OvB−(OvB−Hyd)(R/R0)øn wherein PP is pore pressure, OvB is the overburden value associated with the drilling location, Hyd is hydrostatic pore pressure, R is a measured value of resistivity, R0 is the resistivity at a reference depth or is an imposed value of resistivity, and øn is a normalized value of porosity. ## Claims ### Claim 1 A method of estimating pore pressure (PP) of a subsurface at a drilling location, the method comprising: measuring a resistivity value (R0) while drilling in a region having a pore pressure (PP[depth of reference]) that is known or can be approximated at a depth of reference; determining from the resistivity value (R0) and the pore pressure (PP[depth of reference]) at the depth of reference an imposed resistivity value (R0[depth of reference]) at the depth of reference; measuring a resistivity value (R) in an interval of the subsurface from the depth of reference to a depth of the drilling location; calculating, using a processor, the pore pressure (PP) at the drilling location based on the following Formula (I): PP=OvB−(OvB−Hyd)(R/R0[depth of reference])øn wherein PP is the pore pressure, OvB is an overburden pressure value associated with the drilling location, Hyd is hydrostatic pore pressure, R is the measured resistivity value for the interval from the depth of reference to the depth of the drilling location, R0[depth of reference] is the imposed resistivity value at the depth of reference, and øn is a normalized value of porosity; adjusting, using the processors, a drilling operation associated with a new drilling location based on the estimated pore pressure, wherein said adjusting comprises optimizing a number of casing strings in the borehole; and repeating the steps of the method using the depth of the drilling location as a new depth of reference to estimate pore pressure at the new drilling location of the subsurface wherein a pore pressure at the new depth of reference is the estimated pore pressure (PP) at the drilling location. ### Claim 2 (depends on 1) The method of claim 1, wherein adjusting the drilling operation further comprises at least one of adjusting a drilling fluid density and adjusting a drilling trajectory. ### Claim 3 (depends on 1) The method of claim 1, wherein the drilling location comprises a location below an operating drill bit in a borehole. ### Claim 4 (depends on 1) The method of claim 1, wherein the estimated pore pressure is displayed on a graphical user interface. ### Claim 5 A non-transitory computer readable medium comprising instructions to perform a method for pore pressure (PP) estimation at a drilling location of a subsurface, the instructions executable on a processor and comprising functionality for: measuring a resistivity value (R0) while drilling in a region having a pore pressure (PP[depth of reference]) that is known or can be approximated at a depth of reference; determining from the resistivity value (R0) and the pore pressure (PP[depth of reference]) at the depth of reference an imposed resistivity value (R0[depth of reference]) at the depth of reference; measuring a resistivity value (R) in an interval of the subsurface from the depth of reference to a depth of the drilling location; calculating, using a processor, the pore pressure (PP) at the drilling location based on the following Formula (I): PP=OvB−(OvB−Hyd)(R/R0[depth of reference])øn wherein PP is the pore pressure, OvB is an overburden pressure value associated with the drilling location, Hyd is hydrostatic pore pressure, R is the measured resistivity value for the interval from the depth of reference to the depth of the drilling location, R0[depth of reference] is the imposed resistivity value at the depth of reference, and øn is a normalized value of porosity; adjusting, using the processors, a drilling operation associated with a new drilling location based on the estimated pore pressure, wherein said adjusting comprises optimizing a number of casing strings in the borehole; and repeating the steps of the method using the depth of the drilling location as a new depth of reference to estimate pore pressure at the new drilling location of the subsurface wherein a pore pressure at the new depth of reference is the estimated pore pressure (PP) at the drilling location. ### Claim 6 (depends on 5) The non-transitory computer readable medium of claim 5 wherein adjusting the drilling operation comprises at least one selected from the group consisting of adjusting a drilling fluid density and adjusting a drilling trajectory. ### Claim 7 (depends on 5) The non-transitory computer readable medium of claim 5, wherein the drilling location comprises a location below an operating drill bit in a borehole. ### Claim 8 (depends on 5) The non-transitory computer readable medium of claim 5, wherein the estimated pore pressure is displayed on a graphical user interface. ### Claim 9 A downhole tool configured to perform a method for pore pressure (PP) estimation at a drilling location of a subsurface, the downhole tool comprising: a processor; a memory comprising software instructions for enabling the downhole tool under control of the processor to: measure a resistivity value (R0) while drilling in a region having a pore pressure (PP[depth of reference]) that is known or can be approximated at a depth of reference; determine from the resistivity value (R0) and the pore pressure (PP[depth of reference]) at the depth of reference an imposed resistivity value (R0[depth of reference]) at the depth of reference; measure a resistivity value (R) in an interval of the subsurface from the depth of reference to a depth of the drilling location; calculate, using a processor, the pore pressure at the drilling location based on the following Formula (I): PP=OvB−(OvB−Hyd)(R/R0[depth of reference])øn wherein PP is the pore pressure, OvB is an overburden pressure value associated with the drilling location, Hyd is hydrostatic pore pressure, R is the measured resistivity value for the interval from the depth of reference to the depth of the drilling location, R0[depth of reference] is the imposed resistivity value at the depth of reference, and on is a normalized value of porosity; adjust, using the processors, a drilling operation associated with a new drilling location based on the estimated pore pressure, wherein said adjusting comprises optimizing a number of casing strings in the borehole; and repeat the steps of the method using the depth of the drilling location as a new depth of reference to estimate pore pressure at the new drilling location of the subsurface wherein a pore pressure at the new depth of reference is the estimated pore pressure (PP) at the drilling location. ### Claim 10 (depends on 9) The downhole tool of claim 9, wherein adjusting the drilling operation comprises at least one selected from the group consisting of adjusting a drilling fluid density and adjusting a drilling trajectory. ### Claim 11 (depends on 9) The downhole tool of claim 9, wherein the drilling location comprises a location below an operating drill bit in a borehole. ### Claim 12 (depends on 9) The downhole tool of claim 9, wherein the estimated pore pressure is displayed on a graphical user interface.