Biology Enzyme EOR for Low Permeability Reservoirs
- He Liu (Research Inst Petr Expl/Dev) | Zhonghong Zhang
- Document ID
- Society of Petroleum Engineers
- SPE Enhanced Oil Recovery Conference, 19-21 July, Kuala Lumpur, Malaysia
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 4.1.5 Processing Equipment, 2.4.3 Sand/Solids Control, 6.5.2 Water use, produced water discharge and disposal, 5.2.1 Phase Behavior and PVT Measurements, 4.1.2 Separation and Treating, 5.4.1 Waterflooding, 5.8.5 Oil Sand, Oil Shale, Bitumen
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Biology enzyme may change wettablity of rocks, release surface hydrocarbon of formation rock particles, and reduce interfacial tension. These properties may be used to reduce water injection pressure of low-permeability oil reservoirs, to enlarge swept volume and enhance recovery rate. We applied 4 types of biology enzyme solutions with different concentrations ranging from 0.5% to 5.0%, to conduct depressurization experiments on 6 artificial cores and 3 natural cores. When concentration of biology enzyme was 2.0%, injection pressure dropped significantly by 22.6% to 72.7%, averagely a drop of 51.4%. Pilot tests have been carried out based on indoor experiment results, as well as economic factors and operating convenience considerations, and other oilfield experiment parameters references. When volume multiple of injected biology enzyme was chosen to be 0.6%PV, production declination of connected oil wells was controlled and production rose gradually, showing that formation pressure has been restored and biology enzyme has played a part in enhancing the oil recovery rate.
Daqing Chaoyanggou Oilfield is ultra-low permeability oilfield, showing non-Darcy seepage flow property. The water injection pressure is high, and oil well pressure build-up level is low, causing low water-flooding recovery rate.
In order to improve the development effect of Chaoyanggou Oilfield, we started a biology enzyme depressurization stimulation testing zone.
We selected a 6-waterwell and connected 24-oilwell block as a testing well group. The oil-bearing area of the testing well group is 1.26 km2 , average net pay thickness is 11.5m,active porosity is 15.0%,air permeability is 4.2×10-3µm2,initial oil saturation is 54.0%,oil bed temperature is 64.5,and saturation pressure is 5.34MPa.
Conditions of the six water injection wells are: the average water injection pressure is 15.5MPa,daily single well injection rate is 13 m3,a cumulative single well water injection rate is 2.75×104 m3.
The situation of the 24 oil well is: daily single well oil output is 1.4t,combined water cut is 11.7%,cumulative single well oil output is 0.35×104t,cumulative water output is 0.06×104 m3.
I.Biology enzyme performance evaluation
Biology enzyme has extra high ability of releasing reservoir rock particle surface hydrocarbon. It may change wettability of rocks and reduce interfacial tension of rock particle surface, thus reducing the flowing resistance of crude oil in reservoir pores, and obtaining the effect of depressurization stimulation and recovery rate growth.
1. Oil flushing ability evaluation
Combining and agitating crude oil samples and silica sand, before putting in different biology enzyme solution, to observe oil flushing effect. When biology enzyme solution contacts oil-sand, crude oil separates from silica sand surface and formulates floated oil drops and lumps, the sand particle surface turns to be clean and oil water interface is clear, this illustrates that the oil flushing ability of Biology enzyme is rather good.
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