APPLICATION OF NMR TECHNIQUE TO MOVABLE FLUID OF ULTRA-LOW PERMEABILITY AND TIGHT RESERVOIR : A CASE STUDY ON THE YANCHANG FORMATION IN LONGDONG AREA, ORDOS BASIN

作者：REN Yinghui; WU Ke; HE Kangning; WU Guangzhou; ZHU Yalin; WU Hanning; YANG Youyun

来源：矿物岩石, 2017, 37(1).

• NMR
• ultra-low permeability and tight reservoir
• Longdong area
• Yanchang Formation
• movable fluid
• T2cutoff

The T2 distribution of drilling core samples from oil-bearing formation of Yanchang Formation in the Longdong area is studied by use of nuclear magnetic resonance method,and the low limit of throat radius of the cores is determined on the basis of centrifuge tests and the T2 cutoff value of the movable fluid and irreducible fluid is calibrated.It shows that the low limit of centrifugal force for the movable fluid is 2.07 MPa,the low limit of throat radius for movable fluid is 0.07 μm,which is defined by gas water centrifugal Washbumn equation.The NMR analysis for different reservoir types of Chang 6 and Chang 8 indicates that the T2cutoff hardly has correlation with porosity and permeability,even its porosity or permeability is similar,and the core T2cutoff may vary greatly.The difference of T2cutoff is apparent in different reservoir cores.On the whole,the range of T2cutoff distribution of ultra-low permeability reservoir is smaller than that of tight reservoir.In fact,the T2cutoff distribution of ultra-low permeability reservoir is 9.64 ms～16.68 ms while the T2cutoff distribution of tight reservoir is 9.64 ms～24.04 ms.The main reason for this difference is that T2cutoff is not only related to porosity and permeability,but also affected by pore structure,mineral composition and clay types.In addition,the irreducible water saturation has a good correlation with porosity and permeability,with the increase of porosity and permeability,the irreducible water saturation of core is decreased.Meanwhile,the relationship between T2cutoff and T2 spectra is analyzed,and 4 basic rules are summarized.According to the domestic and international oil and gas field development and production experience,combined with the practical situation of Longdong area Yanchang formation,the reservoir in the area is classified by level of movable fluid saturation.It shows that the tight reservoir belongs to class Ⅲ reservoir (movable fluid saturation is in the range of 35％～50％),the ultra low permeability reservoir is the class Ⅱ reservoir (movable fluid saturation is in the range of 50％～65％) and part of the class Ⅲ reservoir.

• 出版日期2017
• 单位西北大学