Development Of Fractures Of Chang 8 Formation In Zhenjing And Its Relationship With The Exploitation

Low permeability reservoirs in Ordos basin generally do not have edge water and bottom water,and they belong to the lithologic deposit.Chang 8 formation of Zhenjing in the south of Tian huan depression is a reservoir with low bearing,low permeability and strong aeolotropism in planar and vertical scale.The exploration evaluation of Zhenjing block started in 1997.Only Chang 8 formation gained plenty of evidence of oil and gas until 2006,and there were not commercial oil and gas flow.Some old wells gained high production because of the use of refracturing in 2007,and some high production wells were drilled.As a result,the exploration and exploitation of Chang 8 formaiton in Zhenjing enter a new stage.In the exploitation,the producing energy is not enough,and daily fluid production rate and daily oil production declined sharply.Pilot flooding tracey is conducted in ZJ5 block,and the overall outcome is good.The effects on the oil wells are not uniform.The water saturation of some wells increase fast.Waterflooding can be seen in some wells.The natural fracture can affect the filtration of oil and gas,because there are aeolotropism in exploitation and discord in outcome.So,the study on fracture developmental discipline and its effect on production can provide significant foundation for the next adjustment of exploitation and well network.This paper use the information of field fractures and the observation of fracuture -s of cores to analyse the fr acuture type,attitude,density and validity etc.The FMI fracture identification is based on the previous work, and continued high electric conductivity fracuture,non-continued high electric conductivity fracuture,continued high electric resistivity fracture,non- continued high electric resistivity fracture are identified.Then,the fracture attitudes and parameters are calculated.Analysing the fractures respond to the conventional log,calculating fracture porosity and width,using the methods of discriminant a nalysis,R/S,PNN,this paper identify the fractures in comprehensive ways.At last,this paper establishes a comprehensive criterion of identification which is based on the conventional log.Based on the previous study of structural evolution about this area,combined with the field investigation,core observation and log interpretation,this paper concludes that the fracture aligements mainly are NEE-SWW,W- E,NE-SW.The aligements are controlled by the Yanshanian and Himalayan regional stress field.The development of natural fractures is controlledby the lithology,bed thickness,fault,etc. Based on the evaluation about distribution of fractures on the plane, the interested area could be divided as three areas, that is, the developed fracture area, the more developed fracture area, and the undeveloped area. Referring to the analysis of producing, this thesis believes that the fractures could play a good role for diversion in the developed fracture areas, and when being fractured, the natural fractures would be extended NEE-SWW and NE-SW. In the later waterflooding,the oil wells along with the fractures are easy to be affected. Because of this,the alignment of input well and corner well should be NEE-SWW, and increase the distance between the wells whose alignments are NEE-SWW.Meanwhile, slow the velocity of the waterflooding, decrease the well array spacing, enhance the response of lateral well,control the injection pressure and injection rate, increase the sweep efficiency. In the area where the fractures are not many, current waterflooding works well,the response of wells are equal. In the next exploitation, app licable injection pressure,injection rate and producing energy should be kept. The interspacing of wells along the fractures should be increased, so the fracturing scale and individual well producing rate will be enlarged. In the area where the fractures does not develop, the oil wells are not easy to be affected in the waterflooding, and the mass production and flow potential of producing wells are bad. Because of this,when the exploitation is made in the area where the fractures are not many, more fracturing should be done in order to enhance the capacity of creating fractures. Increase the drainable area,injection pressure and injection rate, and increase the well spacing density appropriately, change the condition that the oil wells are hard to be affected. The fractures system of the target stratum in the study area has dual effects on the exploitation, so when the adjustment and make of development plan are conducted, the fracture superiority must be utilized, and the waterflooding and channeling should be avoided. The exploitation with high efficiency can be achieved.