Fractured conglomerate gas reservoir protection in evaluation drilling

For drilling the deep fractured carbonate conglomerate reservoir of the third section of Shahejie Formation in Daxing exploration zone of Langgu Sag, drilling mud losses can not be avoided, because of the lack of reservoir sensitivity information and the low pressure gradient of main producing formation. Considering Xing 9 reservoir geological characteristics and the drilling experience in recent years, some measures were taken to prevent drilling fluid leaking, as optimizing well scheme, strengthening the integration of seismic material and geological analysis while drilling, predicting fracture distribution before and after drilling, choosing suitable drilling fluid system according to different geological conditions, and controlling the slurry solid content. This method led to the success of overall drilling 10 wells, with drilling period down to an average of 105 days, and the average single well daily gas production more than 50,000 cubic meters, which indicated the studied method could protect fractured reservoirs and rapidly build up productivity. The successful application proved that the combination of geological and drilling process analysis is critical to solve complex geological problems in this area. Experiences were accumulated of drilling fractured conglomerate gas wells.