Carbonate Reservoir Fracturing Selection for Sustained Conductivity
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Solution Overview
Problem
Hydraulic fracturing in deep and tight carbonate reservoirs is challenging due to high formation closure pressures and varying rock lithology, leading to uncertainties in selecting the appropriate fracturing method, which can result in reduced or non-existent oil and gas flow.
Innovation Solution
A method and system that evaluates rock quality, calculates breakdown pressure envelope, and determines optimal perforation directions using acid or proppant fracturing based on acid fracture conductivity parameters, ensuring fractures propagate into gas-bearing rock areas with sustainable conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If acid fracturing is used in deep and tight carbonate reservoirs, then the operation can be carried out in the field with no risk of screen out and is less expensive, but the fracture conductivity is more difficult to maintain for longer durations especially in high formation closure pressure environments
Solution Approach 1:
The patent applies parameter changes by evaluating multiple formation parameters including acid fracture conductivity parameter, fracture conductivity declining parameter, rock embedment strength, and fracture closure pressure to determine the optimal fracturing method. By changing the selection criterion from simple ease of operation to a multi-parameter evaluation system, the patent resolves the contradiction between operational ease and conductivity maintenance.
Solution Approach 2:
The patent implements feedback through a systematic evaluation process that uses measured formation properties (rock embedment strength, fracture closure pressure) and calculated parameters (acid fracture conductivity parameter, fracture conductivity declining parameter) to feedback into the fracturing method selection. This closed-loop approach allows dynamic adjustment of the fracturing strategy based on actual formation conditions.
2Reliability
If proppant fracturing is used, then fracture conductivity can be maintained under high formation closure pressure, but the operation requires more sophisticated equipment and carries risk of screen out
Solution Approach 1:
The patent uses parameter changes by establishing threshold values for the acid fracture conductivity parameter and fracture conductivity declining parameter to objectively determine when proppant fracturing is necessary. This quantitative approach replaces subjective equipment selection with data-driven decisions, resolving the contradiction between reliability and equipment complexity.
Solution Approach 2:
The patent applies feedback through continuous monitoring and evaluation of formation properties and fracture characteristics. By feedback on the actual fracture conductivity and comparison with predicted values, the system can determine whether proppant fracturing was necessary or if acid fracturing would have sufficed, optimizing the balance between reliability and equipment complexity.
3Productivity
If fractures are initiated at higher breakdown pressure, then fractures can propagate into gas-bearing rock areas, but the required breakdown pressure increases
Solution Approach 1:
The patent applies parameter changes by evaluating rock embedment strength and fracture closure pressure to determine optimal perforation locations and orientations. By changing the approach from brute-force high-pressure fracturing to targeted fracturing based on formation parameters, the patent achieves gas-bearing rock penetration at lower breakdown pressures.
Solution Approach 2:
The patent implements preliminary action through pre-evaluation of formation properties (rock typing, petrophysical properties, geomechanical properties) and calculation of breakdown pressure envelopes before the fracturing operation. This preliminary characterization allows planning of optimal perforation locations and orientations that reduce the required breakdown pressure while ensuring propagation into productive zones.
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 method improves the success of hydraulic fracturing by initiating fractures at lower breakdown pressures and increasing conductivity, enhancing hydrocarbon production in deep and tight carbonate reservoirs.
Implementation Method 1
acid fracturing generates fracture conductivity through acid etching the fracture surface
Data Source
AI summary
Techniques for stimulating a formation surrounding a wellbore include determining a rock type of the formation along the well trajectory in landing zone in terms of measured depth. A depth-specific acid fracture conductivity parameter of the formation and a depth-specific fracture conductivity declining parameter of the formation are determined. One or more depth intervals requiring fracturing are determined based on the rock type of the formation, the acid fracture conductivity parameter of the formation, and the fracture conductivity declining parameter of the formation. A fracturing method is determined for each depth interval of the one or more depth intervals based on the acid fracture conductivity parameter of the formation and the fracture conductivity declining parameter of the formation. A corresponding pump schedule of the fracturing method is determined, and a fluid of the pump schedule is pumped into the wellbore to fracture or stimulate the formation.