Davud Davudov

Formation Damage by Organic Deposition

Abstract Despite the myriad of published literature on asphaltene deposition in porous media, true understanding of its characterization is still lacking. A literature review of the state of the art in asphaltene research is provided, examples and theories involved in asphaltene deposition are expounded, and a discussion about the validation and critiques is conducted in this chapter. This work takes a detailed look at asphaltene deposition within the porous media, and provides a novel technique in the characterization of the deposition problem. Historically, permeability reduction has been attributed to pore volume change due to surface deposition. However, pore throats will also be blocked through retainment of particles that will potentially lead to severe conductivity and permeability reduction even when a large fraction of total pore volume still remains intact. Here we evaluate permeability reduction as a function of the combined effects of surface deposition and interconnectivity loss due to pore blockage. The effects of pore surface deposition and pore blockage are evaluated based on published experimental data on limestone, sandstone, and carbonate rock samples. We observed that surface deposition seems to be dominant in limestone due to the large pore throat size compared to the particle size. In sandstone samples, both the surface deposition and pore throat plugging seem to contribute fairly equally to permeability reduction. In the case of dolomite however, the pore blockage seems to be dominant, which results in an almost instantaneous sharp decrease in sample permeability. This work sheds some light on the inadequacies of the deposition model, and provides a solution for better future modeling work of asphaltene deposition in the near wellbore reservoir zones.

A Special Focus on Formation Damage in Unconventional Reservoirs

Abstract As shale plays maintain their role as one of the main energy resources in the United States, production sustainability remains the key decision-making parameter for investors. Multistage fracturing treatment has made shale resources economically viable; however, the success of production operations depends on the quality of the created fracture network and matrix deliverability around the wellbore. The sharp decline in production usually observed is strongly affected and controlled by a reduction of fracture conductivity and formation deliverability owing to formation-damage mechanisms. Major damaging parameters resulting in fracture conductivity loss such as proppant transport and placement, proppant embedment and crushing, fine migration and plugging, gelling damage, and multiphase flow are analyzed. Moreover, the severe reduction in reservoir permeability is explained by the combination of two main phenomena: (1) Pore shrinkage and (2) connectivity loss due to bond breakage between interconnected pores. We use fractal and percolation theories to analyze the effects of both pore shrinkage and connectivity loss on intrinsic permeability reduction. This study summarizes the vital considerations and important parameters that are crucial to know in order to design successful hydraulic fracture treatments and improve productivity in tight formations.