Drilling Pipe Energy Storage for Deep Borehole Pressure Measurement
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Solution Overview
Problem
The existing methods for measuring in-situ stress in deep boreholes using hydraulic fracturing face significant challenges due to excessive system compliance, leading to inaccurate calculations of the maximum horizontal principal stress, especially when the measurement depth exceeds a few hundred meters, resulting in high errors in reopening pressure measurements.
Innovation Solution
A method involving pumping a fluid into the inner space of a drilling pipe for energy storage, and releasing it through a valve at the lower end to inject fluid into a test interval with a controlled flow rate, minimizing system compliance and improving measurement precision by using the drilling pipe as a high-pressure fluid pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the measurement depth is increased, then the measurement capability is improved, but the system compliance increases leading to measurement error exceeding 100%
Solution Approach 1:
The system is segmented into two separate functions: the drilling pipe serves as a fluid delivery conduit while a dedicated high-pressure pump (separate from the ground pump) provides the pressurization function. This segmentation isolates the compliance of the drilling pipe from the pressure measurement system, allowing deep hole access without compromising measurement accuracy.
Solution Approach 2:
A high-pressure pump acts as an intermediary device between the ground pump and the test interval. This intermediary minimizes the compliance effect by being positioned close to the test interval and using minimal fluid volume, thereby transmitting pressure accurately despite the depth of the borehole.
2Length of stationary object
If the drilling-pipe-type system is used for deep boreholes, then the measurement depth is extended, but the reopening pressure calculation error exceeds 100%
Solution Approach 1:
The pressurization function is extracted from the ground pump system and placed into a dedicated high-pressure pump located at the bottom of the borehole. This extraction removes the source of compliance error from the system, allowing accurate reopening pressure measurements even at great depths.
Solution Approach 2:
The invention uses hydraulic principles by utilizing a high-pressure pump to directly inject fluid into the test interval at the bottom of the borehole. This hydraulic approach eliminates the need to transmit pressure through the entire length of the drilling pipe, thereby minimizing compliance effects and improving measurement precision.
3Measurement precision
If the system compliance is reduced to maintain precision, then the measurement accuracy is improved, but the measurement depth is limited to shallow boreholes
Solution Approach 1:
The solution moves the pressure generation function from the surface (one dimension) to the bottom of the borehole (another dimension). By placing the high-pressure pump at the test interval location, the system achieves both deep hole capability and high precision simultaneously, as the pump creates pressure locally rather than transmitting it through the drilling pipe.
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
This approach allows for accurate determination of the reopening pressure with reduced interference from system compliance, enhancing the precision of in-situ stress measurements in deep boreholes by using the drilling pipe as an energy storage and injection system.
Implementation Method 1
pumping a fluid into an inner space of a drilling pipe for energy storage; and opening a valve at a lower end of the drilling pipe such that energy is released from the fluid in the inner space of the drilling pipe under the action of pressure to inject the fluid into a test interval
Data Source
AI summary
The present disclosure relates to the technical field of rock mechanics, and in particular to a method for accurately measuring a reopening pressure of hydraulic fracturing induced fracture in a deep borehole. The method includes: pumping a fluid into a sealed inner space of a drilling pipe for energy storage; and opening a valve at a lower end of the drilling pipe such that energy is released from the fluid in the inner space of the drilling pipe under the action of pressure to inject the fluid into a test interval. In the method according to the present disclosure, a fluid is pumped into an inner space of a drilling pipe so that the inner space of the drilling pipe is used as a high-pressure fluid pump to inject the fluid in the inner space of the drilling pipe to the test interval until the closed fracture is reopened.