Ceramic-Coated Proppant Composites for High-Stress Fractures
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Solution Overview
Problem
Hydraulic fracturing treatments face challenges due to proppant granules crushing under reservoir closure stress, leading to the generation of fines that reduce fracture conductivity and cause production issues, with existing materials like silica sand being unable to withstand stresses above 6,000 psi without significant damage.
Innovation Solution
A composite is developed with a proppant or sand control particulate core coated with a hardened reaction product made from silica, alkali hydroxide, aluminosilicate, and aluminum trichloride or zinc chloride, which increases the compressive strength and reduces fine generation by enhancing the core's crush resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silica sand is used as proppant, then cost is reduced and availability is improved, but crush resistance is insufficient for stresses exceeding 6,000 psi
Solution Approach 1:
The patent applies composite materials by coating silica sand particles with a ceramic material to create a composite proppant structure. The silica sand core provides low cost and availability, while the ceramic coating layer provides enhanced crush resistance, allowing the proppant to withstand closure stresses exceeding 6,000 psi. This composite approach resolves the contradiction by combining materials with complementary properties.
2Reliability
If proppant granules are used to hold fracture open, then fracture conductivity is improved, but fines are generated when granules crush under closure stress
Solution Approach 1:
The ceramic-coated composite proppant prevents fine generation by providing a hard protective shell around the silica sand core. The ceramic coating has superior mechanical strength and resistance to crushing, which prevents the core material from breaking down into fines under closure stress, thereby maintaining fracture conductivity without generating harmful fine particles.
Solution Approach 2:
The ceramic coating acts as a thin protective shell around the proppant core. This shell is designed to be sufficiently strong to prevent core crushing while maintaining appropriate porosity and surface characteristics to allow fluid flow through the proppant pack, thus protecting the core from generating fines.
3Strength
If stronger proppants are used to withstand higher closure stresses, then crush resistance is improved, but cost and availability are reduced
Solution Approach 1:
The composite structure allows the use of abundant, low-cost silica sand as the core material, which is then enhanced with a thinner layer of expensive ceramic material. This approach provides the high crush resistance of ceramic proppants while using significantly less ceramic material, thereby reducing overall cost and improving availability compared to using solid ceramic proppants.
4Productivity
If proppant is deposited in fracture to create porous bed, then fluid migration ability is enhanced, but proppant pack conductivity is damaged when proppant crushes
Solution Approach 1:
The ceramic-coated composite proppant maintains proppant pack conductivity by preventing proppant crushing. The hard ceramic shell protects the softer silica sand core from breaking under closure stress, preventing the generation of fines that would otherwise plug pore throats and damage conductivity. This ensures long-term maintenance of fluid migration pathways.
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 coated composite significantly reduces fine generation and maintains high fracture conductivity even at elevated closure stresses, extending the use of proppants to formations with stresses up to 12,000 psi and beyond, while minimizing embedment into the rock and reducing proppant flowback.
Implementation Method 1
a hardened reaction product prepared from (a) silica or a silicate; (b) an alkali hydroxide or alkali oxide; (c) an aluminosilicate; and (d) at least one member selected from aluminum trichloride, zinc chloride
Data Source
AI summary
The strength of a proppant or sand control particulate may be improved by coating the proppant to form a composite. The composite has enhanced compressive strength between about 34 to about 130 MPa and minimizes the spalling of fines at closure stresses in excess of 5,000 psi. Conductivity of the proppant pack in the fractures is further enhanced due to the increase in strength of the particles.