Sains
Malaysiana 46(11)(2017): 2163-2167
http://dx.doi.org/10.17576/jsm-2017-4611-17
The
Application of Fractal Dimension on Capillary Pressure Curve to Evaluate the
Tight Sandstone
(Aplikasi
Dimensi Fraktal ke atas Lengkung Tekanan Kapilari untuk Menilai Batu Pasir
Padat)
CHUNHUA GUO1, YU YANG2*,
PING YAN2, RUILI ZHOU3 & XIAODONGPENG4
1College of Environment and Civil
Engineering, Chengdu University of Technology, Chengdu 610059, China
2State Key Laboratory of Oil and
Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu
610059, China
3Petro-Engineering Research
Institute of North China Oil and Gas Branch, Sinopec, Zhengzhou 450006, China
4Research Institute of Zhanjiang
Branch, CNOOC Energy Technology & Services Co. Zhanjiang 524057, China
Diserahkan:
6 Januari 2017/Diterima: 12 Jun 2017
ABSTRACT
The rock of gas tight
reservoir is more heterogeneous than that of conventional sandstone reservoir
and is more prone to water-blockage because of the invasion of operation fluid.
This paper presented a new approach for the analysis of the capillary pressure
curve for tight gas reservoir. Herein, the saturation equation with fractal
dimension proved the previous observation that the log-log plot of capillary
pressure against water saturation is a straight line, which is quite different
from the popular observation by Corey’s correlation. How to transform the
capillary pressure curve to relative permeability curve was also discussed with
fractal dimension. The fractal dimension of capillary pressure, which is not
only an indication of heterogeneity, can also reveal the potential water blocks
in tight gas wells. If the rock has higher fractal dimension, being at the same
water saturation, the capillary pressure will be higher and the relative
permeability of water will be smaller, which means higher injection pressure is
required to displace the trapped water in reservoir. It is suggested that for
the tight gas pay zone with higher fractal dimension, more precautions should
be taken to prevent the water trapping during drilling or stimulating
operation.
Keyword: Capillary pressure
curve; relative permeability; tight sandstone; water trapping
ABSTRAK
Batuan di takungan kedap gas
lebih heterogen daripada takungan batu pasir konvensional dan lebih cenderung
kepada penahanan air kerana pencerobohan daripada cecair operasi. Kertas ini
mengemukakan pendekatan baru untuk analisis lengkung tekanan kapilari takungan
kedap gas. Oleh itu persamaan penepuan dengan dimensi fraktal membuktikan
pemerhatian yang lepas bahawa plot log-log tekanan kapilari terhadap air
penepuan adalah garis lurus dan agak berbeza daripada pemerhatian popular oleh
Pekali Corey. Bagaimana mengubah lengkung tekanan kapilari untuk ketelusan
bandingan lengkung juga dibincangkan dengan dimensi fraktal. Dimensi fraktal
tekanan kapilari bukan hanya sebagai petunjuk kontra, juga boleh mendedahkan
potensi blok air dalam telaga gas yang padat. Jika batuan mempunyai dimensi
fraktal yang tinggi pada penepuan air yang sama, tekanan kapilari akan menjadi
tinggi dan ketertelapan relatif air akan menjadi kecil yang bermaksud tekanan
pancutan yang tinggi diperlukan untuk menggantikan air yang terperangkap dalam
takungan. Adalah disarankan agar zon kaksa kedap gas dengan dimensi fraktal
yang lebih tinggi memerlukan lebih banyak langkah keselamatan untuk mencegah
air daripada terperangkap semasa penggerudian atau operasi perangsang.
Kata kunci: Batu pasir padat; ketertelapan relatif; lengkung
tekanan kapilari; perangkap air
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*Pengarang untuk
surat-menyurat; email: yangyu@cdut.cn
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