Research On Oil/water Distribution Character Of Ordovician Reservoir In 12th West Block Of Tahe Oilfield

The District 12 reservior in Tahe oil field is a overdeep buried fracture-cave oil reservior, its buried depth reachs as deep as 5800m-6500m. With high heterogeneity,and the heavy oil in it,the crude oil average dynamic viscosity is as high as 8067 mPa.s(50℃),the reservior is also a inspissated pool. The oil-water relatioship is very complicated,and develop for oil is very difficult.Based upon practical condition of the western District 12,with the well drilling,well logging,core,testing,development dynamic data and so on, individual well reservoir identification and fluid identification have been made. From the individual well oil/water relationship extend to the oil/water relationship of well tie and the oil/water relationship in the whole plane,get the main recognition as follows:1. There developed fracture-cavity reservoir in western of District 12 in Tahe oilfield on the whole, on the base of analysing development dynamic date, reservoir pressure and analysis of fluid characteristic, discovered that interwell communication is not good.2. The types of individual well reservior mainly include cave, fracture-cave and fracture, propose logging identification sign for each kind of reservoir and resistivity boundary to divide oiliness in these reservoir. The impact of dropping of drilling fluid to distingushing the reservoir oiliness has been discussed: the reservoir with perfect cave has characteristic of high resistivity, the measuration for drilling fluid leakage may largely depend on how much the crude oil in the reservoir openning, water bearing fracture with little oil can't lead to great quantity of leakage.3. The original oil-water distribution in District 12 of Tahe field clarrified into three: oil producing profile,oil-water producing profile and water producing profile. oil-water producing profile refers to drilling profile that may develop oil layer and water layer simultaneously ,regardless of stratum compactum between oil layer and water layer. The well profile oil-water distribution follows the characteristic of up-oil and down-water.4. The breakthrough well mainlly refers to the type of water ratio rising rapidly which depend on the water layer below drilling profile. The type of slowly decline of water ratio actually belongs to drilling leakage or the output of fracturing liquid. 5. The oil-water distribution based on fracture-cavity unit, there is no one same oil/water contact. It is follows to the normal oil-water distribution of up-oil and down-water in the little part of area through analysing well profile and lateral well data. So is in one same fracture-cave unit, but there are several fracture-cave units regionally,and each has oil/water contact respectively, neither is in the whole area or the fracture zone divided at present.6. Ancient karst erosional surface,fault,local structure play an important control role in controlling oil/water distribution. Ancient karst erosional surface control the longitudinal distribution of reservoir openning,and the distribution of fracture-cave reservoir is interrelated with oil-water distrbution. Solution cavity of District 12 of Tahe field is mainly developed in the realm of 0-80m under erosion surface of T74. Corresponding to the distribution of oil-water, as a whole ,there is more oil and little water in the realm of 0-80m under erosion surface ,out of 80m under this surface ,there is almost water . fault and companion fractures are the former passageway for karstification, which increased the contact area between surface water and groundwater and carbonate rock ,also increase erosion area, so improved the seepage of carbonate rock, with the reason, fault zone is karstification zone. Part structure is closely-related with the local water-oil distribution: relative structural high produce oil and relative structural low produce water. Structural depression often produce no oil or gas .7. Water and oil coexist in the inner of the fracture-cavity unit,large or larger fracture belt is the oil abundance zone .It may be that crude oil charge replacement part of the water in the fracture-cave unit in Distrct 12,so there coexist water and oil in fracture-cave unit. Large or larger fault belt can link fracture-cave unit with big reservoir opennings, and fault always are the important passageway for crude oil charge, so these fracture-cave units with big openings is the better passageway of crude oil charge, therefor, large or larger fault belts are the crude oil abundance zones.