The Research On The Characteristicis Of Ordovician In Salt Covered Area Of Southern Tahe Oilfeild

The salt covered area of southern tahe oilfeild is an area that be surrounded by the wedge-out boundary of C1b rock salt and mining right boundary of the southern tahe oilfield of Sinopec. In recent years,the area has formed a S106 borefild, S112 borefild two Ordovician oil and gas development block through a rolling exploration and development. In 2007, the AT5 well that located east of the atan block obtain high and stable yield industrial oil and gas flow in Ordovician, to further strengthen its exploration and development confidence in the vast region.However, the exploration and development have also shown that the reservoir of Ordovician in the region have character of itself,that the types is varied , the genetic mechanism is complex, the heterogeneity of reservoir is high, and take the difficult for further exploration.In this paper, by observing the drill core and sheet, the reservoir pore space of the region of interest is divided into five main categories: porosity, vug, cave, fracture of weathering and tectoclase.According to the differet type of pore space,the rock types,the horizon and the genetic mechanism,the reservoir of Ordovician in the region is divided into reservoir of karst fracture-cave system, reservoir of karst caves , reservoir of dissolved pores, reservoir of fracture, and summarized the response characteristics of the logging of the four types reservoir ,then, the reservoir of nearly 70 wells in the region have been divised.Focusing on the karstification(dissolution)that occurred in salt covered of southern Tahe Oilfield, the author firstly summarized the the karst(dissolution)characteristics of the identification mark in the study area, Secondly, the reservoir-forming mechanism was generalized, by means of studying the controlling factors on the development and distribution of reservoir in the study area, yielding an understanding that, in the study area, the reservoir of dissolved pores followed chemical erosion of atmospheric water mechanism in syn-sedimentary ; The karst vugs at the top of Lianglitage Formation followed the karst of atmospherc water mechanism that dominated the parallelism unconformable surface of theâ…¡action in the middle caledonian Orogeny .The karstic cavernous reservoir controlled by a huge fault trending from north to south, followed the infiltration flow karst mechanism of atmospheric water, however, vug reservoir controlled by the distribution of fractures probably followed the hydrothermal activity mechanism.On the basis of the seismic response of reservoir, attribute analysis, combination of well and seismic data, the author carried out study on the selection of favorable reservoir facies belt, the results show that the karstic cavernous reservoir favorable facies belt is generally present along the S-N trending huge faulted zone mentioned above, presenting a strip-shaped distribution. The vug reservoir controlled by the distribution of fractures favorable facies belt is development of llittle fractures in the region of interest.Evaluation standard on the Ordovician reservoir for the study area was preliminary established, excellent reservoir is mainly distributed along several S-N trending faulted zones.