Reason for Non-Simultaneous Placing in Operation of all Zones in Horizontal Well with Multi-Stage Fracturing

Abstract

The number of zones during multi-stage hydraulic fracturing (MSHF) is increased. There have been cases of MSHF with 10 zones. Therefore, along with such important parameters as number of fractures, fracture length, fracture conductivity there is one more important parameter -the order of placing zones in operation in horizontal wells with MSHF. In this paper, the production of multi-stage hydraulic fracturing wells of one JSC Gazpromneft-NNG oilfield is analyzed and necessary calculations are made which allow to substantiate the placing zones in operation of MSHF well gradually from the bottom to the heel, with carrying out the refracturing the previous zone at the transition to next. Both the cumulative production in case of simultaneous and in case of gradually placing zones in operation is made, and the economic evaluation is carried out. Current stateAt the present time amount of drilling multi-stage hydraulic fracturing wells is increased in JSC Gazpromneft-NNG. Thus, on 01.06.2013 43 horizontal wells with MSHF are drilled on considered oilfield. The average starting up parameters are shown in the table 1. But some questions have been raised during the exploitation of such wells:-Is the interference between fractures in MSHF wells? -Are there pressure losses in constriction of the well? -What to do with the well when productivity would begin to decrease? AnalysisThe wells drilled on the same formation are considered during the analysis. The wells that are obviously have significant influence of the adjacent injection wells have been removed from the analysis. As the result 38 wells were analyzed. All the wells were parted in two groups: the first group -wells with 3 and 4 fracturing zones (18 wells); the second group -wells with 5, 6 and 7 fracturing zones (25 wells). As can be seen from the figure 1 and 2 both groups of well tend to decrease fluid rate, increase production water cut and as the result reduce the oil rates.