The scarcity of reservoir cores and their relatively random properties lead to the application of synthetic samples for scientific research. In this study, a synthetic sandstone preparation method based on organic adhesives was proposed. A cycloaliphatic epoxy resin adhesive was selected as the cementing material. The properties of the additives and the basic mechanism of the reaction between the epoxy resin and the curing agent in the presence of catalyst were described. The workflow of sample preparation was also presented in detail. A series of physical and mechanical tests were conducted to obtain the basic properties of the synthetic samples. The results show that the cores prepared by the current method display relatively good porosity and permeability. Mechanical properties obtained through uniaxial and triaxial tests, tensile tests, and thick-walled cylinder tests indicate that the artificial cores are similar to the natural sandstones. The proposed method can be used to produce synthetic sandstone samples with weak to moderate strength for sand production experiments or related topics in rock mechanics.
Sand production is a common concern in weakly consolidated sandstone reservoirs. An intuitive understanding of sand production mechanism can be obtained through laboratory sand production experiments. However, due to the scarcity and random properties of the full-size reservoir cores, sandstone analogs have become one of the main substitutes in laboratory simulations.
Unconsolidated sandstones can usually be fabricated by the compaction of sand with some clay content (Perera et al., 2017). However, for weakly consolidated sandstones, it is necessary to add some binders to enhance the rock strength. Poland cement has been used in the preparation of weakly consolidated sandstones for sand production simulation (Nouri et al., 2004; Younessi et al., 2012; Vahidoddin et al., 2011). Consolidating sand with Poland cement is a relatively simple method. The basic principle is to use cement as a binder and mix it with natural or quartz sand and water in a certain proportion. After a period of curing, specimens with weak strength can be obtained. Some other binders like alkaline silica gel have also been used to replicate sandstones (den Brok et al., 1997; David et al., 1998). The gel was coated on the sand grains, and then its solvent was burned off. The mixture was placed in a mold and underwent hot pressing under a high pressure of 40 MPa and a high temperature up to 800 °C. The samples made by this method were relatively well consolidated. A similar method was developed with some modifications (Kozhagulova et al., 2018 & 2021). Sodium silicate solution was used to simulate the in-situ cementation of sandstones with ultra-weak strength. The chemical reaction between carbon dioxide and silica solution contributes to the consolidation of the sand. Some other methods have been invented for specific purposes. Sample preparation by firing the mixture of clay and sand has been introduced to the production of synthetic sandstones with rich clay content (Shabdirova et al., 2016). Besides, to produce reconstituted soils, the Calcite In-situ Precipitation System (CIPS) was utilized to replicate the diagenesis of calcite cement by flushing a special solution through the soil, leading to the precipitation of calcite and the forming of calcite bridges at the particle contacts (Ismail et al., 2000).
