METHOD FOR MONITORING SALINITY WITHIN AN UNDERGROUND FORMATION

• US 20190323344A1
• Filed: 11/30/2017
• Published: 10/24/2019
• Est. Priority Date: 12/20/2016
• Status: Active Grant

• Current Assignee: IFP Energies Nouvelles
• Original Assignee: IFP Energies Nouvelles
• Inventors: GARCIA, Bruno, CHERUBINI, Aurelien, DESCHAMPS, Herve, CEREPI, Adrian
• Granted Patent: US 10,801,321 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 43/16 Enhanced recovery methods for obtaining hydrocarbons
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure
• CPC Class Codes: E21B 47/113 using electrical indications; using light radiations
• CPC Class Codes: E21B 49/00 Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
• CPC Class Codes: E21B 49/02 by mechanically taking samples of the soil
• CPC Class Codes: E21B 49/08 Obtaining fluid samples or testing fluids, in boreholes or wells
• CPC Class Codes: E21B 49/0875 determining specific fluid parameters
• CPC Class Codes: G01V 3/26 operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device with electromagnetic waves G01V3/30
• CPC Class Codes: G01V 3/265 Operating with fields produced by spontaneous potentials, e.g. electrochemicals or produced by telluric currents
• CPC Class Codes: G01V 3/38 Processing data, e.g. for analysis, for interpretation, for correction

Abstract

Method of exploiting and/or of monitoring the exploitation of a fluid such as a hydrocarbon fluid present in at least one geologic layer of an underground formation.

From consecutive pressure and spontaneous potential measurements taken at least at one measurement point in at least one well drilled through at least the geologic layer of interest, the slope of a curve showing the evolution of the spontaneous potential gradient as a function of the pressure gradient is determined. Then, from this slope and from a graph representative of the evolution of the electrokinetic coupling coefficient as a function of the salinity for the layer considered, a salinity value is determined at the measurement point.

Claims

1. A method of exploiting and/or of monitoring the exploitation of a fluid such as a hydrocarbon fluid present in at least one geologic layer of an underground formation, at least one well being drilled through at least the layer of the formation, by means of at least one graph representative of the evolution of the electrokinetic coupling coefficient as a function of salinity for the layer, wherein the salinity within at least the layer is determined at least at one measurement point located in the well and at the level of the layer for at least one predefined time Ti of the exploitation of the fluid, by carrying out at least the following steps:

a) measuring a pressure at the measurement point for at least the time Ti, a time Ti−

1 preceding the time Ti and a time Ti+1 following the time Ti,

b) measuring a spontaneous potential at the measurement point for the times Ti−

1, Ti and Ti+1,

c) from the pressure measurements and the spontaneous potential measurements for the times Ti−

1, Ti and Ti+1 at the measurement point, determining the slope of a curve showing the evolution of the spontaneous potential gradient as a function of the pressure gradient between the times Ti−

1 and Ti+1, and

d) from the slope and the graph, determining a value for the salinity at the measurement point and at the time Ti,

and in that the fluid is exploited and/or the exploitation of the fluid is monitored by taking account of the value of the salinity.

2. A method as claimed in claim 1, wherein the graph is determined beforehand by performing, in the laboratory and using a rock sample representative of the geologic layer, pressure and spontaneous potential measurements for a plurality of salinity values of a brine saturating the sample.

3. A method as claimed in claim 1, wherein the well is a production well, an injection well or a well intended for monitoring the exploitation of the fluid.

4. A method as claimed in claim 1, wherein the pressure measurements and the spontaneous potential measurements are taken at least at two measurement points in at least two wells drilled through at least the layer of the formation, and an evolution of the salinity is determined in the layer between the two wells.

5. A method as claimed in claim 1 wherein, in addition to the value of the salinity, an absolute permeability value is determined for the layer by performing, in addition to the pressure measurements and the spontaneous potential measurements, measurements of the flow rate of the exploited fluid at least at the measurement point and for at least the times Ti, Ti−

1 and Ti+1.

6. A method as claimed in claim 1 wherein, in addition to the value of the salinity, a relative permeability value is determined at the measurement point by performing, in addition to the pressure measurements and the spontaneous potential measurements, electrical resistivity measurements at least at the measurement point and for at least the times Ti, Ti−

1 and Ti+1.