利用人造岩石样品开展地震岩石物理实验研究的新进展

Progresses of rock physics laboratory study based on synthetic rock samples

人造岩石样品被用于油气勘探开发诸多环节中,在岩石物理学、岩石力学、油层物理等领域中取得了广泛应用。做为天然岩石的补充和有效替代样品,人造岩石在科学研究和工程应用中发挥着重要作用,为理解和分析复杂地层中油气赋存和运移、地球物理响应、物理化学机制等方面发挥重要作用。本文介绍了胶结法、烧结法、冷压法和热压法、3D打印技术、降温加压法等人造岩石样品的实验工艺,总结了针对复杂油气储层开展人造砂岩、双孔隙岩石、人造页岩、人造碳酸盐岩、天然气水合物模拟等实验方法,以及应用人造岩石样品开展地震波散射机制、地震各向异性、地震波衰减、震电效应、波致流机制、页岩脆性和甜点、水合物声电和力学等实验研究的进展。通过对人造岩石样品研究现状及发展趋势的总结表明,人造岩石样品与天然岩石具有越来越高的相似性,针对砂岩、含裂缝岩石、页岩、碳酸盐岩及天然气水合物等多种非常规储层的岩石类型,可以模拟孔隙度、渗透率、孔隙特征、矿物组分、流体饱和状态、微观结构等多种复杂岩石特征,参数可控的人造岩石样品可以实现单一物理量的变化,开展流体渗流、弹性性质、电磁学性质、力学性质等多方面的研究,定量的表征孔隙流体运移、弹性波传播、电场磁场、岩石破裂等多种物理化学过程中的机制,为降低油气勘探开发中的多解性、提高油气勘探开发精度提供支撑。利用人造岩石样品与天然岩石相结合开展研究可更好地揭示岩石物性对岩石物理特征的影响,但仍然存在一些问题。岩石力学性质与岩石孔隙结构、岩石矿物成分、岩石颗粒粒径、胶结方式和胶结强度等都有关,目前人造岩心在这方面的模拟还不太理想。同时,随着非常规复杂储层逐渐成为了目前油气勘探开发的主要目标,储层岩石的物性特征更加复杂,对人造岩石样品的模拟精度提出了更高的要求。与天然岩石相比,人造岩石样品有一些固有的不足,如孔隙结构相对比较单一、胶结方式和强度与天然岩石有差异、孔隙度和渗透率相对较高等,因此还需要在实验工艺上进一步提高人造岩石与天然岩石的相似程度。

Synthetic rock samples are widely used during oil exploration and production in rock physics,rock mechanics and petrophysics to simulate natural rock in the case of the lack of adequate natural rock samples or an alternative solution mimicking natural rock characteristics.Hence,the synthetic rock samples can help to investigate hydrocarbon accumulation and migration,geophysical characteristics and the physical and chemical mechanisms in reservoir rocks.We review the experimental methodologies used to construct synthetic rock samples including cementation,sintering,cold/hot pressing,3D printing and the cooling-pressing process.Based on these methodologies,synthetic samples are used to mimic sandstone,fractured porous rocks,shales,carbonates and gas hydrate.Synthetic rock samples can be used in experiments on seismic scattering,anisotropy,attenuation,seismo-electric effects,wave-induced fluid flow mechanism,shale brittleness and sweet point analysis,elastic/electric/mechanic properties of gas hydrate,etc.Synthetic rock samples present more and more similarity to natural rocks in pore structure,porosity,permeability,pore characteristics,mineral components,fluid saturation,micro-structure,etc.When focusing on unconventional reservoir rocks,such as tight sandstone,fractured rocks,shales,carbonates and gas hydrate,synthetic rocks with controlled parameters can provide samples with a single variable to investigate fluid flow,elastic properties,electromagnetism properties,mechanical properties.These can be used to quantitatively characterize the fluid flow transportation,elastic wave propagation,electromagnetism field,rock failure and other physical or chemical mechanisms,hence help to reduce the ambiguity and improve the accuracy in hydrocarbon exploration and production.Together with natural rocks,using synthetic rocks can reveal the effects of rock properties on rock physics characteristics.However,the application of synthetic rocks for rock mechanics laboratory study still has some limitations.The rock mechanics properties related to pore structure,mineral components,grain size,cementation,etc.,synthetic rocks are not yet reliable enough to simulate natural rock mechanics characteristics.Meanwhile,the main targets for petroleum exploration and production are becoming unconventional reservoirs with more complex reservoir properties.Hence the feasibility and accuracy of simulating reservoir rocks with comprehensive complexities should be closely examined during laboratory study based on synthetic rocks.In general,synthetic rock still has some intrinsic drawbacks compared to natural rock(simple pore structure,different cementation,comparatively high porosity and permeability,etc.).Techniques for construction synthetic rock should be updated to improve the similarity between synthetic and natural rocks and to enhance the feasibility of using synthetic rock for laboratory study and industrial production.