Comparative study on sanding characteristics between weakly consolidated sandstones and unconsolidated sandstones

摘要

Sand production is a common phenomenon during the extrusion of hydrocarbons, which reduces production efficiency and brings about safety problems. A detailed knowledge of sanding process is essential for targeted sand control. This paper aims at investigating the sanding characteristics of weakly consolidated sandstones and unconsolidated sandstones by comparative methods. We conducted sanding experiments on artificial cores of different consolidation degrees and performed numerical studies based on explicit finite element method. We found that hole failure mode, sanding form and the particle size distribution of the produced sand are three typical features distinguishing sand production of weakly consolidated sandstones from that of the unconsolidated ones. Macroscopically, the weakly consolidated sandstones tended to develop localized failure with mainly rock pieces produced while the unconsolidated one failed uniformly with almost loose grains produced. On the particle scale, the sand produced by weakly consolidated sandstone showed better uniformity and lower fine particle content relative to the original sample while the unconsolidated sandstone produced sand with practically the same size as the original core. We suggest that cohesion is the dominant factor that affects sanding characteristics and post-peak strain softening is critical to the simulation of realistic hole failure. The results further reveal the differences of sand production between the two sandstones, and can provide some theory support for the sand production in oil and gas field.