Study On The Geological Characteristics And Production Influencing Factors Of Heshui Nanchang 7 Reservoir

Tight oil has played an important role in the global energy structure as conventional oil and gas production continues to decline.China's tight oil reserves are huge.Due to the poor physical properties of tight sandstone reservoirs,it must be reformed by fracturing to improve reservoir physical properties to increase single well production.There are some problems such as large difference in single well production in the Chang7 Member tight sandstone reservoir of south area of Heshui in Ordos Basin.On the basis of the core observations and test data of physical property of reservoirs,the superimposition styles of sand bodies in the study area have been characterized.And then,the reservoir characteristics are analyzed by means of the casting thin sections,scanning electron microscopy,nuclear magnetic resonance and CT test.Finally,the author analyzes the factors affecting per-well production by fracturing fluid damage experiment and production data.The main research results are as follows:(1)The Chang7 Member reservoir in the study area is mainly composed of three main types of gravity flow sand bodies:turbidite,landslide and sandy debris flow sand body.The sandy debris flow sand body is most developed.According to the thickness of the sand body,the logging characteristics,the shale sandwich,etc.,the superimposition styles of sand bodies in this study area is divided into eight shapes such as a stacked box type,a superimposed box type and an isolated box type.(2)The main lithology is fine grained feldspathic lithic sandstone and lithic feldspar sandstone,medium separation,sub prism of grinding roundness,low-medium maturity degree.The interstitial materials content is distributed between 14%and 15%.The main clay minerals are illite and chlorite,the average porosity is 7.8%and the permeability is 0.0985mD.(3)The porosity of the Chang 7 reservoir is poor,the main pore type is the dissolution pore of feldspar and debris,the pore throat is small,and the connectivity is poor.The sand bodies of different superimposition styles have been evaluated,combining with the reservoir characteristics.The results show that A1(cut-up box type),A2(superimposed box type)and A4(isolated box type)are excellent sand body superimposition styles,as A3(toothed box type),B(bell type+box type)is good,and C2(bell type+funnel type)is relatively poor.(4)Single well production is controlled by multiple influencing factors.The oil and gas production of box sand body is generally higher than the bell type and funnel sand body.The sand body with large thickness,good physical condition and small mud content has a good production.The damage of the slick water fracturing fluid to the reservoir is lower than the guar gum fracturing fluid,and exploitation using the slick water fracturing fluid can obtain relatively high production.The influence of single fracturing construction parameters on production is not obvious.