Method for determining pore pressure in oil and gas wells using basin thermal characteristics

Patent metadata

Field	Value
Publication number	US-2016376887-A1
Application number	US-201615191604-A
Country	US
Kind code	A1
Filing date	Jun 24, 2016
Priority date	Jun 26, 2015
Publication date	Dec 29, 2016
Grant date	—

Abstract

This inventive method provides a novel way of modeling basins in planning the drilling of crude oil and natural gas wells by accounting for thermodynamic considerations in tracking the pore pressure of a location of interest. By plotting the energy gradients, heat flux, and thermal conductivity of the location of interest, the user can more accurately identify the location of the Top of Geopressure and additional pertinent information during the well drilling planning process that can reduce costs and increase the safety of the process.

First claim

1 . A method for modeling a potential well basin,
wherein it is assumed that when the energy available to perform work equals zero, the well depth point measured is at its equilibrium; wherein it is understood that at said equilibrium state, the plot of pore pressure of the well at a particular depth point will generate a curve with a slope equal to a measure of energy per unit volume, which will be defined as the additional pore pressure that is induced by temperature at said depth point; said method comprising:
(a) determining the resistivity of the various depth points recorded for the location of the potential well basin;
(b) creating a graph that plots the resistivity of the potential well basin against the depth of the basin, wherein the normal compaction trend line is also plotted on the same graph;
(c) creating a graph that plots the pressure of a potential well basin against the depth of the basin by calculating the pressure at the various depth points plotted on the said resistivity against depth plot;
(d) defining the top of the geopressure to be the start of the transition between equilibrium and the abnormally pressured zones;
(e) defining the transition zone as the point between the top of the geopressure and the bottom of the geopressure;
(f) determining the slopes of energy gradient within said transition zone to determine the number of different pressure regimes within the transition zone;
(g) relating the resistivity of the particular depth point to the thermal energy, wherein that relation is then rewritten in the terms of its thermal equivalent;
(h) calculating formation pore pressure at the various depth points previously considered and evaluating using the DWC method;
(i) normalizing the data generated for the DWC method and the previously generated pressure data;
(j) plotting the normalized DWC method generated line on the same plot as the previously generated pressure versus temperature line;
(k) determining the lithology composition of the location of interest;
(l) calculating the heat flux and thermal conductivity of the proposed well based upon the lithology composition;
(m) determining the top of geopressure to be the point at which the two equilibrium energy lines intersect for the first time;
(n) entering the top of geopressure, pressure, and other thermal conditions into a basin simulator to generate the simulated basin for planning.

2 . The method of claim 1 , wherein the resistivity of the various depth points is determined through resistivity logging.

3 . The method of claim 1 , wherein the basin is manually simulated.

4 . The method of claim 2 , wherein the resistivity logging is performed using wire-line or logging while drilling systems.

5 . A method for locating a hydrocarbon reservoir while drilling,
wherein it is assumed that when the energy available to perform work equals zero, the well depth point measured is at its equilibrium; wherein it is understood that at said equilibrium state, the plot of pore pressure of the well at a particular depth point will generate a curve with a slope equal to a measure of energy per unit volume, which will be defined as the additional pore pressure that is induced by temperature at said depth point; said method comprising:
(a) determining the resistivity of the various depth points recorded for the location of the potential well basin;
(b) creating a graph that plots the resistivity of the potential well basin against the depth of the basin, wherein the normal compaction trend line is also plotted on the same graph;
(c) creating a graph that plots the pressure of a potential well basin against the depth of the basin by calculating the pressure at the various depth points plotted on the said resistivity against depth plot;
(d) defining the top of the geopressure to be the start of the transition between equilibrium and the abnormally pressured zones;
(e) defining the transition zone as the point between the top of the geopressure and the bottom of the geopressure;
(f) determining the slopes of energy gradient within said transition zone to determine the number of different pressure regimes within the transition zone;
(g) relating the resistivity of the particular depth point to the thermal energy, wherein that relation is then rewritten in the terms of its thermal equivalent;
(h) calculating formation pore pressure at the various depth points previously considered and evaluating using the DWC method;
(i) normalizing the data generated for the DWC method and the previously generated pressure data;
(j) plotting the normalized DWC method generated line on the same plot as the previously generated pressure versus temperature line;
(k) determining the lithology composition of the location of interest;
(l) calculating the heat flux and thermal conductivity of the proposed well based upon the lithology composition;
(m) determining the top of geopressure to be the point at which the two equilibrium energy lines intersect for the first time;
(n) identifying the point of peak amplitudes of the thermal conductivity and heat flux;
(o) defining the depth point of the peak amplitudes of thermal conductivity and heat flux to be the location of a hydrocarbon reservoir.

Assignees

• Univ Louisiana At Lafayette

Inventors

• Hayatdavoudi Asadollah
• Odubayo Sadiq

Classifications

• E21B2200/20

  Computer models or simulations, e.g. for reservoirs under production, drill bits · CPC title

• E21B43/00

  Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells (applicable only to water E03B) · CPC title

• E21B47/06 Primary

  Measuring temperature or pressure · CPC title

• G01V2210/00

  Details of seismic processing or analysis · CPC title

• E21B49/003 Primary

  by analysing drilling variables or conditions (E21B49/005 takes precedence; systems specially adapted for monitoring a plurality of drilling variables or conditions E21B44/00) · CPC title