地质科技通报 (May 2022)
Experimental study on sweep pattern of heavy oil reservoirs with variable speed drive based on different geological models
Abstract
The heavy oil reservoirs in marine sandstone in the east of South China Sea are generally characterized by loose cementation, strong bottom water, complex interlayer distribution and low recovery degree.Therefore, the existing conventional water flooding experiments can not accurately describe the sweep law of heavy oil in single wells. Based on the geological characteristics of heavy oil reservoir in the PY oilfield, an improved physical simulation experiment of bottom horizontal plate water flooding is designed.It is applied to comprehensively study the sweep law of single well and the recovery degree of heavy oil, considering reservoir rhythm, interlayer development scale and liquid extraction time. The experimentresults are showed as following.①Interbeds developed in homogeneous rhythm and positive rhythm reservoirs transform the original bottom water drive into secondary edge water drive. The longer the well spacing of interbeds is, the stronger the inhibition of bottom water coning is. In addition, the remaining oil located in the lower transition zone, middle to small pore throat in the middle and upper zones and near the interbeds can be effectively displaced by multiple amplitude controll and fluid extraction due to gravity differentiation.In this case, the single well sweep coefficient can be enhanced. The sweep efficiency can be increased by 34.1%-54.9% after adopting 4-stage variable speed to control amplitude and extract liquid during ultra-high water cut stage. Through multiple amplitude control and liquid extraction in z1680 homogeneous rhythm reservoir and z1610 positive rhythm reservoir, the daily oil production can be increased to 2-3 times of that before liquid extraction, and the production effect is good. ②For the reverse rhythm reservoir with a range of 5-10, the permeability difference between the top and bottom is significant. Thus, it is easy to form a high permeability channel at the top. The development length of interlayer and the change of liquid extraction method have little effect on the sweep range. Through multiple amplitude control and liquid extraction, the production effect of z1640 reverse rhythm reservoir is not obvious. The research results can provide solutions for the optimization of liquid production structure and the formulation of liquid extraction methods in heavy oil reservoirs with different geological models.
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