Experimental Study On Lateral Seepage Mechanism And Displacement Characteristics Of Reef Limestone Reservoirs In LH11-1 Oilfield

The reef limestone is one king of biogenetic originated carbonate reservoir, mostly developed in marine sedimentary environment. Considering the rare study on filtration theory in limestone reefreservoirs, especially when it comes to the relative permeability curves featured vuggy-porous formation. Long core experiments were conducted using cores deprived from the horizontal direction in which vuggy-porous pores are well developed. As a result, the relative permeability curves were obtained.Furthermore, filtration theories involved in the horizontal direction was studied.Currently, most relative permeability curves are primarily focused on short cores, whereas, due to the fact that short cores are less representative than long cores in respect to the capability to simulate the underground situation, relative permeability curves acquired from long cores can be more authentic. To achieve that purpose, some tests were carried out on long core composed of 12 short cores in which cavern-porous media is well developed. Even more, the residue oil distribution was determined by Coulomb method. This study shows that oil phase relative permeability declines very fast comparing to the much slower increase of the water phase. It also indicates that the end point value of the water phase is extremely small, besides, the two phase area is narrow.(1) We observed pore structures of some representative cores in a microscopic view, besides, we analyzed contents of clay and measured connectivity between pores and throats which, no doubts, have an impact on recovery ratio.(2) Some relative permeability curves were obtained characterized by different porous feature and different permeability. At the same time, filtration theories exposed in the above cores are also discussed.(3) Under the guidance of some principal rules we have already knew, we conducted some long core experiments with short cores from different formations of the same reservoir under reservoir conditions in order to analyze filtration theory involved in water/oil displacement.(4) Other tests like displacement experiments in full diameter core and tests regarding stress sensitive were also carried out as a way to facilitate finding out factors affecting flow properties.From all the work above, we can deepen our understanding relevant to theories involved in water/oil displacement in the horizontal direction of limestone reef reservoirs. Meanwhile, residue oil distribution after displacement are also understood in a better way. Which in turn, will help oil exploration in limestone reef reservoirs in a more efficient and reasonable manner.