During fluid injection into a multilayered reservoir,a different pressure gradient is generated across the face of each permeable layer.This pressure gradient generates driving forces in the wellbore during well shut-...During fluid injection into a multilayered reservoir,a different pressure gradient is generated across the face of each permeable layer.This pressure gradient generates driving forces in the wellbore during well shut-in that causes the injected fluid moves from higher pressure layers to lower pressure layers,a phenomenon known as interwell cross-flow.Cross-flow behavior depends on the initial pressure in the permeable layers and may be referred to as natural cross-flow(identical or natural initial pressures)and forced cross-flow(different initial pressures because of exploitation).Cross-flow may induce sand production and liquefaction in the higher pressure layers as well as formation damage,filter cake build-up and permeability reduction in the lower pressure layers.Thus,understanding cross-flow during well shut-in is important from a production and reservoir engineering perspective,particularly in unconsolidated or poorly consolidated sandstone reservoirs.Natural and forced cross-flow is modeled for some injection wells in an oil reservoir located at North Sea.The solution uses a transient implicit finite difference approach for multiple sand layers with different permeabilities separated by impermeable shale layers.Natural and forced cross-flow rates for each reservoir layer during shut-in are calculated and compared with different production logging tool(PLT)measurements.It appears that forced cross-flow is usually more prolonged and subject to a higher flow rate when compared with natural cross-flow,and is thus worthy of more detailed analysis.展开更多
文摘During fluid injection into a multilayered reservoir,a different pressure gradient is generated across the face of each permeable layer.This pressure gradient generates driving forces in the wellbore during well shut-in that causes the injected fluid moves from higher pressure layers to lower pressure layers,a phenomenon known as interwell cross-flow.Cross-flow behavior depends on the initial pressure in the permeable layers and may be referred to as natural cross-flow(identical or natural initial pressures)and forced cross-flow(different initial pressures because of exploitation).Cross-flow may induce sand production and liquefaction in the higher pressure layers as well as formation damage,filter cake build-up and permeability reduction in the lower pressure layers.Thus,understanding cross-flow during well shut-in is important from a production and reservoir engineering perspective,particularly in unconsolidated or poorly consolidated sandstone reservoirs.Natural and forced cross-flow is modeled for some injection wells in an oil reservoir located at North Sea.The solution uses a transient implicit finite difference approach for multiple sand layers with different permeabilities separated by impermeable shale layers.Natural and forced cross-flow rates for each reservoir layer during shut-in are calculated and compared with different production logging tool(PLT)measurements.It appears that forced cross-flow is usually more prolonged and subject to a higher flow rate when compared with natural cross-flow,and is thus worthy of more detailed analysis.
