Study On Interwell Connectivity Of Tahe Fracture-cavity Reservoir

Tahe oilfield is an unconventional reservoir with karst caves and fractures as the main reservoir space and seepage channel formed by multi-phase tectonic movement and paleokarst.The heterogeneity is extremely strong,and the random development of the fracture-cavity system makes the reservoir interwell connectivity problem is extremely complicated.As one of the key development blocks of Tahe oilfield,Tahe 12 district is facing a severe problem that the watercut in the well area rises and the oil production decreases sharply.The decrease of oil well production is affected by factors such as energy decline and water intrusion,therefore,it is of great significance for the efficient development of oil fields to correctly understand the underground connection of the reservoir and the flow law of the fluid.It is of great significance for oilfield development.Taking the AD4 well area in the 12th district of Tahe as an example,the dynamic and static research methods are used to analyze the connectivity and water intrusion of the block,and the mechanism model analysis and actual model numeIical simulation are carried out to analyze the complexities of interwell connectivity between multiple sets of reservoirs.Firstly,eombined with the geological model,the use of pressure trend analysis,production interference,injection-production relationship and other methods to analyze the dynamic connectivity between wells are used,then calculate the AD4 area reserves in units of well groups.Secondly,the water influx and water volume of typical wells were calculated by the production indicator curve method,the deficit volume curve method and the pressure fall method.For the actual block,improve the calculation method of water influx,and use improved methods to calculate parameters such as water intrusion index and water body size.According to the flow law and production situation of the fluid,the oil-water migration relationship and the connecting parts of these wells are studied.Finally,based on the static and dynamic connectivity and fluid flow laws in the comprehensive comparison well area,the two typical connectivity modes are established.One is a single hole connects with water at the bottom,another is cavity-crack-lytic hole connection mode also connects with water at the bottom.The effects of connectivity between wells on reservoir production law are analyzed from the factors of connectivity,water intrusion index and connectivity location.Combined with numerical simulation,the production rules of actual blocks are fitted,appling the production indicator curve and water drive curve which obtained by the mechanism model to the actual block,the complex connectivity between multiple sets of storage groups in the AD4 block is obtained,which provides more intuitive guidance for the understanding of connectivity.