Abstract:

Based on the braided river system analysis and reservoir distribution characteristics of the Sulige large tight sandstone gas field, the concept of reserves concentration is proposed and four sand-body distribution models are established, namely the thick block, vertical overlapping panconnected, dispersed partially-connected, and dispersed types. Reservoir recovery of horizontal wells under different sand-body combination is analyzed, and technical measures to improve the recovery rate of horizontal wells are proposed. The results show that straight wells is imperfect due to the blocking zones present in compound sand body of the braided river sedimentary system.Horizontal well can overcome the blocking zone influence and increase the degree of reserve exploitation within the layer.However, the scattered distribution of layered sand bodies and the horizontal well development will lead to insufficient vertical bearing department of gas reserves, and thereby reducing the degree of interlayer recovery. For the greater reserves concentration, thick block and multi-vertical overlapping panconnected types and horizontal well development can significantly improve the degree of reserve exploitation and recovery, of which over 70% are Ⅰ+Ⅱ wells. For the disperse partially connected reservoirs with lower reserve concentration, development of vertical well pattern and optimization of the horizontal well distributions can improve the recovery by more than 10%.

Key words: tight gas, reservoir distribution, Sulige gas field, horizontal well, recovery ratio