TITLE:
Application of Multi-Attribute Crossplots to Tight Gas in X Area, Western China
AUTHORS:
Lifang Cheng, Yanchun Wang, Zhiguo Li, Fei Li, Fuxiu Gong
KEYWORDS:
Multi-Attribute Crossplots, Mathematical Statistics, Tight Sandstone Gas, Fluid Identification
JOURNAL NAME:
Open Journal of Geology,
Vol.6 No.4,
April
19,
2016
ABSTRACT: The gas-bearing reservoir
in X area is mainly the tight sandstone reservoir characterized by low porosity
and permeability, frequently lateral variation and poor connectivity of single
sand. The previous research results reveal that the general seismic attributes
analysis cannot meet the requirement of fluid identification. This is because
the relationship between seismic attributes and their implication is uncertain
and ambiguous, which decreases the precision of both reservoir prediction and
fluid identification. To overcome the problem, multi-attribute crossplot
technology is proposed from the mathematical statistical point of view rather
than the correspondence between the seismic attributes and their geological
implication. In this method, the wells which have the same statistical law are
classified firstly, and then all the interest wells are retained while the
wells beyond the statistical law are eliminated, and the seismic attributes
sensitive to the same types of eliminated wells are optimized and used to
generate crossplots. The nonzero area of their crossplots results just predicts
the potential distribution. The discontinuity of subsurface geological
conditions results in the non-continuous shape and the seismic bin lead to the
mosaic form. The optimization of sensitive attributes relative to the same
types of wells is independent from each other, and thus the order of attributes
in crossplots does not affect the final prediction results. This method is
based on the statistical theory and suitable for the areas such as the study
area abundant of lots of well data. Application to X area proves the
effectiveness of this method and predicts plane distribution about different
types of gas production. Due to the effect of faults and other geological
factors, the partition prediction results using multi-attribute crossplots
reach 95% of coincidence which is obviously and far higher than the results of the
whole area. The final prediction results show that the potential areas with
medium and high gas production are mainly concentrated in the northern part of
the study area, where lots of development research will be strengthened.