Abstract:

The gas reservoir in 2^nd member of Shaximiao Formation of Xinchang Gas Field is tight, and its natural productivity is low. As one of the effective development methods, the horizontal wells has unclear main controlling factors of recovery factor. By the numerical simulation software, ECLIPSE, this problem has been analyzed and its influence has been quantitatively evaluated, so as to provide a favorable theoretical basis for the further development by horizontal wells. The results show that: 1）The main controlling factors of tight sandstone gas reservoir changes with the different reserves. For the class Ⅰ, Ⅲ and Ⅳ, it is mainly controlled by the water saturation, while for the class Ⅱ, effective thickness contributes most. 2）The influence of main controlling factors on the recovery factor of horizontal wells are different, with a degree of 91.14 %, 54.33 %, 61.82 % and 45.18 % respectively for class Ⅰ~Ⅳ and multiple factors instead of single factor. 3）The physical properties of reservoir have great influence on the recovery factor of horizontal wells. For the class Ⅰ and Ⅱ reservoir with good properties, the influence degree is less than 1 %, while that of the class Ⅲ and Ⅳ reservoir with poor properties is up to 17 %. Therefore, effective development of horizontal wells depend on the classification of reservoir by different reserves. For the areas with good properties, the optimization of engineering design should be strengthened, like increasing the length of horizontal section and fine fracturing; on the contrary, for that of poor properties, the deployment location of horizontal wells should be chosen in the areas with low water saturation, large effective reservoir thickness and high permeability.

Key words: tight sandstone gas reservoir, horizontal well, recovery factor, water saturation, effective thickness