Investigation on Characteristics and Affecting Factors of Water Cut in Planar Thief Zone

A Unified Parameter to Represent Reservoir Heterogeneity

10.2118/208630-stu ◽

2021 ◽

Author(s):

Nandana Ramabhadra Agastya

Keyword(s):

Water Saturation ◽

Pressure Ratio ◽

Universal Method ◽

Permeability Ratio ◽

Initial Water ◽

Vertical Permeability ◽

Radar Chart ◽

Horizontal Permeability ◽

Water Cut ◽

Thief Zone

Abstract We aim to find a universal method and/or parameter to quantify impact of overall heterogeneity on waterflood performance. For this purpose, we combined the Lorenz coefficient, horizontal permeability to vertical permeability ratio, and thief zone permeability to average permeability ratio, with a radar chart. The area of the radar chart serves as a single parameter to rank reservoirs according to heterogeneity, and correlates to waterflood performance. The parameters investigated are vertical and horizontal permeability. Average porosity, initial water saturation, and initial diagonal pressure ratio are kept constant. Computer based experiments are used over the course of this entire research. We conducted permeability studies that demonstrate the effects of thief zones and crossflow. After normalizing these parameters into a number between 0 and 1, we then plot them on a radar chart. A reservoir's overall degree of heterogeneity can be inferred using the radar chart area procedure discussed in this study. In general, our simulations illustrate that the larger the radar chart area, the more heterogenous the reservoir is, which in turn yields higher water cut trends and lower recovery factors. Computer simulations done during this study also show that the higher the Lorenz coefficient, the higher the probability of a thief zone to exist. Simulations done to study crossflow also show certain trends with respect to under tonguing and radar chart area.

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Identification of the Thief Zone Using a Support Vector Machine Method

Processes ◽

10.3390/pr7060373 ◽

2019 ◽

Vol 7 (6) ◽

pp. 373

Author(s):

Cheng Fu ◽

Tianyue Guo ◽

Chongjiang Liu ◽

Ying Wang ◽

Bin Huang

Keyword(s):

Support Vector Machine ◽

High Water ◽

Identification Accuracy ◽

Support Vector ◽

Machine Model ◽

Machine Method ◽

Support Vector Machine Method ◽

High Water Cut ◽

Water Cut ◽

Thief Zone

Waterflooding is less effective at expanding reservoir production due to interwell thief zones. The thief zones may form during high water cut periods in the case of interconnected injectors and producers or lead to a total loss of injector fluid. We propose to identify the thief zone by using a support vector machine method. Considering the geological factors and development factors of the formation of the thief zone, the signal-to-noise ratio and correlation analysis method were used to select the relevant evaluation indices of the thief zone. The selected evaluation indices of the thief zone were taken as the input of the support vector machine model, and the corresponding recognition results of the thief zone were taken as the output of the support vector machine model. Through the training and learning of sample sets, the response relationship between thief zone and evaluation indices was determined. This method was used to identify 82 well groups in M oilfield, and the identification results were verified by a tracer monitoring method. The total identification accuracy was 89.02%, the positive sample identification accuracy was 92%, and the negative sample identification accuracy was 84.375%. The identification method easily obtains data, is easy to operate, has high identification accuracy, and can provide certain reference value for the formulation of profile control and water shutoff schemes in high water cut periods of oil reservoirs.

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Comparison of Acrylamide and Agar Gels by Freeze-Etching

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100080456 ◽

1977 ◽

Vol 35 ◽

pp. 606-607

Author(s):

Russell L. Steere ◽

Eric F. Erbe

Keyword(s):

Electron Microscope ◽

Sodium Hydroxide ◽

Sodium Hypochlorite ◽

Chromic Acid ◽

Distilled Water ◽

Thin Sheets ◽

Acid Cleaning ◽

Agar Gels ◽

Freeze Etching ◽

Water Cut

Thin sheets of acrylamide and agar gels of different concentrations were prepared and washed in distilled water, cut into pieces of appropriate size to fit into complementary freeze-etch specimen holders (1) and rapidly frozen. Freeze-etching was accomplished in a modified Denton DFE-2 freeze-etch unit on a DV-503 vacuum evaporator.* All samples were etched for 10 min. at -98°C then re-cooled to -150°C for deposition of Pt-C shadow- and C replica-films. Acrylamide gels were dissolved in Chlorox (5.251 sodium hypochlorite) containing 101 sodium hydroxide, whereas agar gels dissolved rapidly in the commonly used chromic acid cleaning solutions. Replicas were picked up on grids with thin Foimvar support films and stereo electron micrographs were obtained with a JEM-100 B electron microscope equipped with a 60° goniometer stage.Characteristic differences between gels of different concentrations (Figs. 1 and 2) were sufficiently pronounced to convince us that the structures observed are real and not the result of freezing artifacts.

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