Acoustic Shock Wave Perforation for Openhole Stress Testing
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Solution Overview
Problem
Conventional openhole formation stress testing, pressure transient testing, and fluid sampling methods are hindered by drilling-induced formation damage, which causes high formation breakdown pressure and impermeability issues, making it difficult to obtain accurate subterranean formation parameters in permeable and low-permeability formations.
Innovation Solution
A tool assembly utilizing electrically induced focused acoustic shock waves to create perforation tunnels, reducing near wellbore stresses and establishing fluid/pressure communication paths across damaged zones, allowing conventional straddle packers to maintain differential pressure and enabling effective testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional straddle packers are used for formation stress testing in openhole sections, then the testing procedure is simple and equipment is readily available, but the packers cannot hold the necessary differential pressure to overcome high formation breakdown pressure caused by drilling-induced formation damage
Solution Approach 1:
The patent applies preliminary action by creating perforation tunnels through the formation before conducting the stress test. These pre-formed tunnels reduce near-wellbore stresses and provide pathways for fluid flow, enabling conventional packers to successfully hold differential pressure during subsequent testing operations.
2Stability of the object's composition
If drilling mud is used to balance formation pressures during drilling operations, then borehole stability is ensured and cuttings are carried to surface, but drilling-induced formation damage occurs that increases formation breakdown pressure
Solution Approach 1:
The patent converts the harmful effect of drilling-induced formation damage into a beneficial outcome by using the damaged zone as a target for perforation tunnel creation. The pre-formed tunnels in the damaged zone reduce near-wellbore stresses and facilitate fluid communication, ultimately enabling successful stress testing that would otherwise be impossible.
3Productivity
If conventional openhole stress testing methods are used in formations with high formation breakdown pressure, then equipment simplicity is maintained, but the tests cannot reach the period required to determine fracture closure pressure
Solution Approach 1:
The patent applies preliminary action by creating perforation tunnels through the formation before conducting the stress test. These pre-formed tunnels reduce near-wellbore stresses and provide pathways for fluid flow, enabling conventional packers to successfully hold differential pressure during subsequent testing operations.
4Productivity
If drilling-induced formation damage zones are present, then drilling operations can proceed normally, but fluid/pressure communication across the damaged zones is blocked
Solution Approach 1:
The patent introduces perforation tunnels as intermediary structures that bridge the borehole and the formation across the damaged zones. These tunnels serve as mediators that restore fluid and pressure communication pathways that were blocked by the drilling-induced formation damage, enabling successful formation testing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The tool assembly effectively reduces formation breakdown pressure, facilitates successful openhole formation stress testing, pressure transient testing, and fluid sampling by establishing communication paths through damaged zones, overcoming the limitations of conventional methods.
Implementation Method 1
A tool assembly utilizing electrically induced focused acoustic shock waves to create perforation tunnels
Implementation Method 2
a pump, for creating hydraulic pressurisation forces
Implementation Method 3
a pressure sensor arranged for measuring a pressure within the isolated section
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3c
AI summary
There is described a tool assembly (1) for performing formation stress testing in an open-hole section of a borehole (501), wherein the openhole section of the borehole (501) is to be provided with, or already have been provided with, a perforation tunnel (504) generated by means of a series of electrically induced focused acoustic shock waves, the tool assembly (1) comprising: - at least two borehole isolation means (2a, 2b) arranged with an axial distance there-between for forming an isolated section (502) at the openhole section of the borehole (501); - a pump device (8) adapted to be in fluid communication with the isolated section (502), wherein the pump device (8) is configured to alter a pressure within the isolated section (502); - a pressure sensor (6c) arranged for measuring a pressure within the isolated section (502); - a control unit (7) to control a testing sequence; - an acoustic shock wave device (4) adapted to generate the series of electrically induced focused acoustic shock waves in order to excavate the perforation tunnel (504); and - an acoustic shock wave sub (3) for actuating the acoustic shock wave device (4). There is also described a method for performing stress testing using such a tool assembly (1).