DAS METHOD OF ESTIMATING FLUID DISTRIBUTION

• US 20170260849A1
• Filed: 03/08/2017
• Published: 09/14/2017
• Est. Priority Date: 03/09/2016
• Status: Active Grant

• Current Assignee: Conocophillips Company (ConocoPhillips)
• Original Assignee: Conocophillips Company (ConocoPhillips)
• Inventors: FRIEHAUF, Kyle, GIBSON, Mark R.
• Granted Patent: US 10,465,501 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• CPC Class Codes: E21B 47/0224 using seismic or acoustic means
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: E21B 47/07 Temperature
• CPC Class Codes: E21B 47/101 using acoustic energy
• CPC Class Codes: E21B 47/102 using electrical indications: using light radiations
• CPC Class Codes: E21B 47/107 using acoustic means
• CPC Class Codes: E21B 47/135 using light waves, e.g. infrared or ultraviolet waves
• CPC Class Codes: G01B 11/161 by interferometric means
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01K 11/32 using changes in transmittance, scattering or luminescence in optical fibres
• CPC Class Codes: G01V 1/226 Optoseismic systems
• CPC Class Codes: G01V 1/40 specially adapted for well-logging

Abstract

This disclosure describes a method of calculating fluid distribution from a hydraulically fractured well, especially during a plug-and-perf hydraulic fracturing operation. The Distributed Acoustic Sensing (DAS) data is used to quantify the fluid distribution in separate perf clusters during fracturing, and the result can be used for completion design and optimization, hydraulic fracturing, and ultimately for oil and gas production.

Claims

1. A method of optimizing fracturing in a well, the method comprising:

a) recording distributed acoustic sensing (DAS) noise intensity signals from a well during a fracturing operation;

b) deriving DAS intensity traces from the recorded DAS noise intensity signals, wherein each said DAS intensity trace is a recording of DAS noise intensity over a span of a pre-determined number of fiber depths averaged over a predetermined period of time, and wherein each said trace do not overlap with other said traces on fiber depths;

c) locating a baseline channel having no perforations at that fiber depth;

d) calculating a volumetric flow rate Q for each said perforation cluster using the following equation;

2. The method of claim 1, wherein the Intensity is directly proportional to a pump-work factor (W) represented by:

Intensity=C₃·

W

3. The method of claim 2, wherein the pump-work factor W is calculated by the following equation:

W=C₁·

Δ

_P·

Q

wherein C₁ is a constant, Δ

_P is the pressure differential between both sides of the perforation.

4. The method of claim 3, wherein the pressure differential Δ

_P is calculated by the following equation;

5. The method of claim 1, further comprising step b-1) prior to step c):

b-1) identifying cluster locations based on fiber depths of each said perforation cluster inside said well.

6. A system for calculating volumetric flow rate through one or more perforation clusters inside a wellbore, comprising:

a) a distributed acoustic sensing (DAS) monitoring device including a optical fiber that runs along the length of the wellbore, wherein the DAS optical fiber is coupled to an interrogating unit for emitting interrogating signals, the DAS monitoring device detects DAS noise intensity signals when strain or temperature deforms the optical fiber;

b) a computer coupled to the DAS monitoring device for recording DAS noise intensity signals detected by the DAS monitoring device;

c) wherein the computer performs the following steps to obtain volumetric flow rates of the hydraulic fluid through each said perforation cluster;

i) deriving DAS intensity traces from the recorded DAS noise intensity signals, wherein each said DAS intensity trace is a recording of DAS noise intensity over a span of a pre-determined number of fiber depths averaged over a predetermined period of time, and wherein each said trace do not overlap with other said traces on fiber depths;

ii) locating the fiber depths of each said perforation cluster inside said well;

iii) locating a baseline channel having no perforation in that fiber depth for each said trace;

iv) calculating a volumetric flow rate Q for each said perforation cluster using the following equation;

7. The system of claim 6, wherein the Intensity is directly proportional to a pump-work factor (W) represented by:

Intensity=C₃·

W

8. The system of claim 7, wherein the pump-work factor W is calculated by the following equation:

W=C₁·

Δ

_P·

Q

wherein C₁ is a constant, Δ

_P is the pressure differential between both sides of the perforation.

9. The system of claim 8, wherein the pressure differential Δ

_P is calculated by the following equation;

10. A method of plug and perf fracturing a well, the method comprising:

a) recording distributed acoustic sensing (DAS) noise intensity signals from a well during a first stage of a plug and perf fracturing operation in said well;

b) deriving DAS intensity traces from the recorded DAS noise intensity signals, wherein each said DAS intensity trace is a recording of DAS noise intensity over a span of a pre-determined number of fiber depths averaged over a predetermined period of time, and wherein each said trace do not overlap with other said traces on fiber depths;

c) identifying the fiber depths of each said perforation cluster inside said well;

d) locating a baseline channel having no perforations at that fiber depth;

e) calculating a volumetric flow rate Q for each said perforation cluster using the following equation;

11. The method of claim 10, wherein the Intensity is directly proportional to a pump-work factor (W) represented by:

Intensity=C₃·

W

12. The method of claim 10, wherein the pump-work factor W is calculated by the following equation:

W=C₁·

Δ

_P·

Q

wherein C₁ is a constant, Δ

_P is the pressure differential between both sides of the perforation.

13. The method of claim 11, wherein the pressure differential Δ

_P is calculated by the following equation;

14. A system for calculating volumetric flow rate in a perforation cluster inside a wellbore undergoing hydraulic fracturing process that injects hydraulic fluids into the wellbore, comprising:

a) a distributed acoustic sensing (DAS) monitoring device including a optical fiber that runs along the length of the wellbore, wherein the DAS optical fiber is coupled to an interrogating unit for emitting interrogating signals, the DAS monitoring device detects DAS noise intensity signals when mechanical strain causes deformation to the optical fiber;

b) a computer coupled to the DAS monitoring device for recording DAS noise intensity signals detected by the DAS monitoring device;

c) wherein the computer performs the following steps to obtain volumetric flow rates of the hydraulic fluid through each said perforation cluster;

i) deriving DAS intensity traces from the recorded DAS noise intensity signals, wherein each said DAS intensity trace is a recording of DAS noise intensity over a span of a pre-determined number of fiber depths averaged over a predetermined period of time, and wherein each said trace do not overlap with other said traces on fiber depths;

ii) locating the fiber depths of each said perforation cluster inside said well;

iii) locating a baseline channel having no perforation in that fiber depth for each said trace;

iv) calculating a volumetric flow rate Q for each said perforation cluster using the following equation;

15. The system of claim 14, wherein the Intensity is directly proportional to a pump-work factor (W) represented by:

Intensity=C₃·

W

16. The system of claim 15, wherein the pump-work factor W is calculated by the following equation:

W=C₁·

Δ

_P·

Q

wherein C₁ is a constant, Δ

_P is the pressure differential between both sides of the perforation.

17. The system of claim 16, wherein the pressure differential Δ

_P is calculated by the following equation;