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首页> 外文会议>SPE/ISRM rock mechanics conference (Oil Rock 2002) >Quantifying Rock Capillary Strength Behavior in Unconsolidated Sandstones
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Quantifying Rock Capillary Strength Behavior in Unconsolidated Sandstones

机译：定量未固结砂岩中的岩石毛细强度行为

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Changes in water saturation or rock wettability can lead tornrock instability and sand production. The effects of saturationrnon rock strength have two origins - chemical sensitivity andrnchanges in capillary forces. In this paper, a detailed study ofrncapillary rock strength behavior after water breakthrough isrncarried out for four different models. These four modelsrnaccount for particle-particle interactions and include sphericalrnparticles in tangential contact, differently sized spheres inrntangential contact, squeezed contacts, and detached spheres.rnThe effects of fluid properties (e.g. contact angle and surfacerntension), rock properties (e.g. particle size, size ratio, contactrnfabric), and deformation of loaded rock on capillary strengthrnhave been mathematically expressed and quantified.rnThe model calculations indicate:rn1. For all the models, capillary strength increases linearlyrnwith increasing surface tension between fluid phases.rn2. Contact angle influences both the magnitude of capillaryrnstrength and its variation with saturation. The larger therncontact angle, the lower the magnitude (under the samernwater saturation) and the faster its decrease withrnincreasing saturation.rn3. If the particle size is uniform, small particle size results inrnhigh capillary strength. If particles have different sizes,rnthe size ratio of the particles has a similar influence onrncapillary strength as does fluid contact angle: it affectsrnboth the magnitude of capillary strength and its variationrnwith water saturation. However, the relationships arerndifferent: the smaller the size difference, the higher thernmagnitude and the slower its decrease with saturation.rn4. For the detached and squeezed models the capillary forcern(or strength) firstly increases with water saturation, thenrndecreases after a critical saturation, in contrast to therntangential contact model where capillary force alwaysrndecreases with water saturation.rn5. Through the introduction of the strain concept into therncapillary models, they can be used to describe capillaryrnstrength variations with rock deformation. It is found thatrncapillary strength more-or-less reaches a maximum whenrnspheres are tangentially contacted, and decreases in bothrnthe squeezed and detached states, but decreasing muchrnfaster with increasing deformation in the squeezed state.rnThese improvements in the micromechanical modeling ofrnsands will be used to build our understanding of sandrnproduction in very weak or unconsolidated rocks, clarifyingrnhow sand production is affected by changes in saturation.
机译：含水饱和度或岩石润湿性的变化会导致岩石不稳定和出砂。饱和度，非岩石强度的影响有两个根源：化学敏感性和毛细作用力的变化。本文对四种不同模型进行了水渗透后毛细岩强度行为的详细研究。这四个模型考虑了颗粒与颗粒之间的相互作用，包括切向接触的球形颗粒，切向接触的大小不同的球，挤压接触和分离的球。流体特性（例如接触角和表面张力），岩石特性（例如粒径，尺寸比）的影响，接触织物）和载荷岩石在毛细管强度上的变形已被数学表示和量化。模型计算表明：rn1。对于所有模型，毛细管强度随着流体相之间的表面张力的增加而线性增加。接触角既影响毛细管强度的大小，又影响其饱和度的变化。接触角越大，（在相同的水饱和度下）幅度越小，随着饱和度的增加其减小的速度越快。如果粒度均匀，则小粒度会导致毛细管强度过高。如果颗粒的大小不同，则颗粒的大小比对毛细管强度的影响与流体接触角的影响相似：它既影响毛细管强度的大小，也影响其随水饱和度的变化。然而，它们之间的关系是不同的：尺寸差越小，幅值越高，随着饱和度的减小幅度越慢。对于分离和挤压模型，毛细作用力（或强度）首先随水饱和度增加，然后在临界饱和度后减小，这与切向接触模型相反，毛细力总是随水饱和度而减小。通过在毛细血管模型中引入应变概念，可以将其用于描述岩石变形引起的毛细强度变化。研究发现，当球体切向接触时，毛细管强度或多或少达到最大值，在挤压状态和分离状态下毛细强度均减小，但随着挤压状态下形变的增加，毛细强度减小得更快。这些改进的砂型微机械模型将用于构建我们对非常软弱或松散的岩石中砂的产生的了解，阐明了饱和度变化如何影响砂的产生。

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