Abstract:

The minor principal stress of Sulige gas field was between 43 ~ 48 MPa, while the proppant always used in fracturing was 20/40 mesh ceramic with moderate strength. In order to evaluate the feasibility of replacing the ceramsite with the quartz sand, we analyzed the demand and current situation of fracture conductivity by numerical modeling and well testing data. On this basis, we studied the selection of quartz sand and the mixed mode of quartz sand and ceramsite by indoor experiments, thus proposing the corresponding plan and carrying out the field tests. The results showed that, firstly, the present fracture conductivity was about 130 μm ²·cm, which was higher than the demand of the reservoir in class I（94 μm ²·cm）, the reservoir in class Ⅱ（65 μm ²·cm） and the reservoir in class Ⅲ（25 μm ²·cm）. The quartz sand was available for fracturing. Secondly, the uniform mixing of the 20/40 mesh quartz sand and ceramsite was a good combination way of proppant. When the closing pressure was between 40 ~ 50 MPa and the proppant placement concentration was 10 kg/m ², the conductivity of these who in the proportion of 1∶0, 7∶3, 1∶1, 3∶7 respectively were 20 % ~ 46.7 %, 23.9 % ~ 56.7 %, 46 % ~ 74.6 %, 73 % ~ 89.7 % of that of ceramsite. Thirdly, the optimal mixed proportion of quartz sand and ceramsite for the reservoir in class I should be below 1∶1. The optimal mixed proportion for the reservoir in class Ⅱ should be below 7∶3. The quartz sand could be used throughout for reservoir in class Ⅲ.

Key words: Sulige, tight sand, gas reservoir, hydraulic fracturing, quartz sand