Productivity Testing Design Method of Multi-Factor Control for Unconsolidated Sandstone Gas Reservoir

Reservoir safety, testing-string safety, and flow control are key factors that should be considered in deep-water unconsolidated sandstone gas well testing work system. Combined with the feature of testing reservoir, pipe string type and sea area, the required minimum testing flow rate during cleaning up process, as well as minimum test flow rate without hydrate generation, pipe string erosion critical production, the maximum testing flow rate without destroying sand formation and the minimum output of meeting the demand of development was analyzed;based on the above critical test flow rates, testing working system is designed. Field application showed that the designed work system effectively provided good guidance for field test operations;no sand production or hydrate generation happened during the test process;the test parameter evaluated the reservoir accurately;the safe and efficient test operation was achieved.

Fluid flow with compaction and sand production in unconsolidated sandstone reservoir

The fluid flow of unconsolidated sandstone reservoir can be affected by compaction and sand production which will damage the reservoir and affect oil well productivity.This study aims to measure how the two factors affect the fluid flow.Firstly,single-phase displacement test was applied to investigate how the permeability changed with compaction.Then two-phase displacement test assessed the influence of compaction on oil production.Finally,the characteristics of fluid flow with compaction and sand production were studied under different water content.The results demonstrate that the reduction of permeability with compaction is irreversible,which will result in lower productivity.In contrast,sand production can increase the permeability at mid and high water content,which slows down the decline of oil production.Generally,the oil well productivity is reduced because of compaction even with sand production,especially when the formation pressure drop varies from 2MPa to 4MPa.Consequently,advance water injection is necessary to keep the formation pressure and oil production during oilfield development of unconsolidated sandstone reservoir.Simultaneously,the study can provide theoretical basis and references for the similar reservoirs.

Porothermoelastic response of an oil sand formation subjected to injection and micro-fracturing in horizontal wells

Stimulation of unconsolidated formations via horizontal wells has seen its vast implementation in the recent development of heavy oil reservoir to save the time and cost of preheating the reservoir before the steam-assisted gravity drainage(SAGD)process.A mathematical approach was proposed in this research that fully couples the hydraulic,mechanical and thermal responses of unconsolidated sandstone formations and also applies failure criteria for describing either shear dilation or tensile parting mechanism that generates microcracks.The approach was implemented to predict the porothermoelastic response of a pair of SAGD wells subject to injection and subsequent micro-fracturing using hot water.It was found that the predicted bottom hole pressures(BHPs)match closely with the field observed data.An elliptical dilation zone developed around the dual wells with relatively high pore pressure,porosity,permeability and temperature,implying good interwell hydraulic communication between both wells.The activation of microcracks dramatically accelerated the dissipation of pore pressure across the entire formation depth and also facilitated heat convection in between the dual wells,though to a lesser extent.In summary,the approach provides a convenient means to assist field engineers in the optimization of injection efficiency and evaluation of interference among multiple horizontal wells.