Euripides Papamichos

In a cased hole gravel pack completion, perforations are packed with proppant to both mechanically support the perforation cavity, and to filter any produced sand before it reaches the surface. Poor perforation packing sometimes occurs in which the perforation is partially or completely unsupported, leading to earlier productivity reduction than in cases of good packing. We investigated productivity reduction and the associated mechanisms in a series of hollow cylinder experiments on outcrop and field cores with varying proppant packing. Packed perforations maintained significantly higher productivity than unsupported perforations by preventing macroscopic shear failure around the cavity and erosion due to sand production. Partial packing may in some instances maintain productivity almost as well as complete packing, but this likely depends on perforation orientation. Compaction tests and numerical simulations suggest that compaction failure is unlikely at the cavity wall in the current experiments, and that proppant-formation interface damage or proppant filtering of produced sand are more probable explanations for the productivity reduction seen in packed perforations.

The flow of reactive fluids into porous media, a phenomenon known as reactive infiltration, is important in natural and engineered systems. While most of the studies in this area cover theoretical and experimental analyses in linear acid flow, the present work concentrates on radial flow conditions from a wellbore in the field and on finding exact analytical solutions to moving boundary problems of the uniform dissolution front. Closed-form solutions are obtained for the transient convection–diffusion which allow the demarcation of the range of applicability of the quasi-static limit. The fluid velocity dependency of the diffusion–dispersion coefficient is also examined by comparing results from analytical solutions from constant and velocity-dependent coefficients. These contributions form the basis for linear stability analyses to describe acid fingering encountered in reservoir stimulation.

Sand production in a perforated sample is determined by the onset of a significant discrepancy between strains in two orthogonal directions. The onset is also analyzed by three different sanding models, i.e., shear failure, cohesive tensile failure, and the effective plastic strain (EPS) models, respectively. Comparing these results, we conclude that the results with the shear failure criterion provide the most conservative prediction, and the EPS can provide the closest results to the testing one, given adequate plastic yielding and sanding parameters. Comparing with the cylindrical cases (open hole), both the plastic radius and critical strains calculated for the perforated cavity (cased hole) cases are calculated. A critical equivalent plastic displacement (EPD) is proposed as only one additional parameter is required on top of those from a typical elastoplastic model and such a criterion allows us to determine the sanding onset directly, those using stress, strength or strain whereas can only be indicated or interpreted indirectly, yet difficult to measure in practices.

Experimental results from sand production hollow cylinders tests are presented for cavity failure and sand production quantification. The effects of important parameters such as the sandstone class, stress rate, fluid flow rate, and time are presented and show how they influence sand production. A model for hydro-mechanical erosion of porous rocks is presented as it is applied to the sand production problem in hydrocarbon production. The model is based on a continuum theory for erosion, which regards the continuum as a three-phase medium and establishes a set of mass balance equations for the various phases. The solution requires an additional equation in the form of a constitutive or evolution law for the sand rate. Erosion is coupled with the mechanical behavior of a sand-producing cavity, and leads to enlargement of the erosion zone. Finally, multiphase flow and its effect on sand production is presented experimentally and theoretically by analyzing water invasion in the sand production test.