Stabilized Water-Cut in Carbonate Naturally Fractured Reservoirs With Bottom Water With an Implication in Well Spacing Design for Recovery Optimization

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Samir Prasun ◽  
Andrew K. Wojtanowicz
Keyword(s):  
Final Stage ◽  
Bottom Water ◽  
Fractured Reservoirs ◽  
Capillary Forces ◽  
Naturally Fractured Reservoirs ◽  
Oil Displacement ◽  
Well Spacing ◽  
Constant Rate ◽  
Water Coning ◽  
Water Cut

Abstract Maximum stabilized water-cut (WC), also known as ultimate water-cut in a reservoir with bottom-water coning, provides important information to decide if reservoir development is economical. To date, theory and determination of stabilized water-cut consider only single-permeability systems so there is a need to extend this concept to naturally fractured reservoirs (NFRs) in carbonate rocks—known for severe bottom-water invasion. This work provides insight of the water coning mechanism in NFR and proposes an analytical method for computing stabilized water-cut and relating to well-spacing design. Simulated experiments on a variety of bottom-water hydrophobic NFRs have been designed, conducted, and analyzed using the dual-porosity/dual-permeability (DPDP) commercial software. They show a pattern of water-cut development in NFR comprising the early water breakthrough and very rapid increase followed by water-cut stabilization stage, and the final stage with progressive water-cut. The initial steply increase of water-cut corresponds to water invading the fractures. The stabilized WC production stage occurs when oil is displaced at a constant rate from matrix to the water-producing fractures. During this stage, water invades matrix at small values of capillary forces so they do not oppose water invasion. In contrast, during the final stage (with progressing water cut), the capillary forces grow significantly so they effectively oppose water invasion resulting in progressive water cut. A simple analytical model explains the constant rate of oil displacement by considering the driving effect of gravity and viscous forces at a very small value of capillary pressure. The constant oil displacement effect is confirmed with a designed series of simulation experiments for a variety of bottom-water NFRs. Statistical analysis of the results correlates the duration of the stabilized WC stage with production rate and well-spacing and provides the basis for optimizing the recovery. Results show that stabilized water-cut stage does not significantly contribute to recovery, so the stage needs to be avoided. Proposed is a new method for finding the optimum well spacing that eliminates the stabilized WC stage while maximizing recovery. The method is demonstrated for the base-case NFR.

Stabilized Water-Cut in Carbonate Naturally-Fractured Reservoirs With Bottom Water With an Implication in Well Spacing Design for Recovery Optimization

2018 ◽  
Author(s):  
Samir Prasun ◽  
A. K. Wojtanowicz
Keyword(s):  
Final Stage ◽  
Bottom Water ◽  
Fractured Reservoirs ◽  
Capillary Forces ◽  
Naturally Fractured Reservoirs ◽  
Oil Displacement ◽  
Well Spacing ◽  
Constant Rate ◽  
Water Coning ◽  
Water Cut

Maximum stabilized water-cut (WC), also known as ultimate water-cut in a reservoir with bottom-water coning, provides important information to decide if reservoir development is economical. To date, theory and determination of stabilized water-cut consider only single-permeability systems so there is a need to extend this concept to Naturally Fractured Reservoirs (NFRs) in carbonate rocks — known for severe bottom water invasion. This work provides insight of the water coning mechanism in NFR and proposes an analytical method for computing stabilized water-cut and relating to well-spacing design. Simulated experiments on a variety of bottom-water hydrophobic NFRs have been designed, conducted, and analyzed using dual-porosity/dual-permeability (DPDP) commercial software. They show a pattern of water cut development in NFR comprising the early water breakthrough and very rapid increase followed by water cut-stabilization stage, and the final stage with progressive water-cut. The initial steply increase of water-cut corresponds to water invading the fractures. The stabilized WC production stage occurs when oil is displaced at a constant rate from matrix to the water-producing fractures. During this stage water invades matrix at small values of capillary forces so they do not oppose water invasion. In contrast, during the final stage (with progressing water cut) the capillary forces grow significantly so they effectively oppose water invasion resulting in progressive water cut. A simple analytical model explains the constant rate of oil displacement by considering the driving effect of gravity and viscous forces at a very small value of capillary pressure. The constant oil displacement effect is confirmed with a designed series of simulation experiments for a variety of bottom-water NFRs. Statistical analysis of the results correlates the duration of the stabilized WC stage with production rate and well-spacing and provides the basis for optimizing the recovery. Results show that stabilized water-cut stage does not significantly contribute to recovery, so the stage needs to be avoided. Proposed is a new method for finding the optimum well spacing that eliminates the stabilized WC stage while maximizing recovery. The method is demonstrated for the base-case NFR.

scholarly journals Study on oil displacement efficiency of offshore sandstone reservoir with big bottom water

2021 ◽  
Author(s):  
Jie Tan ◽  
Ying-xian Liu ◽  
Yan-lai Li ◽  
Chun-yan Liu ◽  
Song-ru Mou
Keyword(s):  
Bottom Water ◽  
High Water ◽  
Displacement Efficiency ◽  
Oil Displacement ◽  
Oil Displacement Efficiency ◽  
Sandstone Reservoir ◽  
Sandstone Reservoirs ◽  
High Water Cut Stage ◽  
High Water Cut ◽  
Water Cut

AbstractX oilfield is a typical sandstone reservoir with big bottom water in the Bohai Sea. The viscosity of crude oil ranges from 30 to 425 cp. Single sand development with the horizontal well is adopted. At present, the water content is as high as 96%. The water cut of the production well is stable for a long time in the high water cut period. The recoverable reserves calculated by conventional methods have gradually increased, and even the partial recovery has exceeded the predicted recovery rate. This study carried out an oil displacement efficiency experiment under big water drive multiple to accurately understand an extensive bottom water reservoir's production law in an ultra-high water cut stage. It comprehensively used the scanning electron microscope date, casting thin section, oil displacement experiment, and production performance to analyze the change law of physical properties and relative permeability curve from the aspects of reservoir clay minerals, median particle size, pore distribution, and pore throat characteristics. Therefore, the development law of horizontal production wells in sandstone reservoirs with big bottom water is understood. It evaluates the ultimate recovery of sandstone reservoirs with big bottom water. It provides a fundamental theoretical basis and guidance for dynamic prediction and delicate potential tapping of sandstone reservoirs with big bottom water at a high water cut stage.

Seismic, geologic, geomechanics, and dynamic constraints in flow models of unconventional fractured reservoirs: Example from a south Texas field

2019 ◽  
Vol 38 (2) ◽  
pp. 116-122 ◽  
Author(s):  
Reinaldo J. Michelena ◽  
James R. Gilman ◽  
Christopher K. Zahm
Keyword(s):  
Multiple Scales ◽  
Fractured Reservoirs ◽  
Flow Simulation ◽  
South Texas ◽  
Naturally Fractured Reservoirs ◽  
Flow Models ◽  
Dynamic Constraints ◽  
Well Spacing ◽  
Orientation Statistics ◽  
The Impact

We present a workflow to build permeability models for flow simulation in unconventional naturally fractured reservoirs constrained by 3D seismic, geologic data and concepts, geomechanics observations, and dynamic data. Joints and faults are modeled separately to account for their differences in scale and flow properties. Seismic-derived orientation statistics are compared against orientations from outcrops and microseismic data to assess their validity and consistency across multiple scales. We show the impact of natural fractures and stress orientation in the flow and variability of the pressure field around producing wells in an unconventional reservoir from south Texas. Such variability can have a significant impact on well interference and optimal well spacing.

scholarly journals Experimental study on waterflooding development of low-amplitude reservoir with big bottom water

2021 ◽  
Author(s):  
Yanlai Li ◽  
Jie Tan ◽  
Songru Mou ◽  
Chunyan Liu ◽  
Dongdong Yang
Keyword(s):  
Bottom Water ◽  
Water Injection ◽  
Water Reservoir ◽  
High Water ◽  
Recovery Factor ◽  
Low Viscosity ◽  
Well Spacing ◽  
High Water Cut Stage ◽  
High Water Cut ◽  
Water Cut

AbstractFor offshore reservoirs with a big bottom water range, the water cut rises quickly and soon enters the ultra-high water cut stage. After entering the ultra-high water cut stage, due to the influence of offshore production facilities, there are few potential tapping measures, so it is urgent to explore the feasibility study of artificial water injection development. The quasi-three-dimensional and two-dimensional displacement experiments are designed using the experimental similarity criteria according to the actual reservoir parameters. Several experimental schemes are designed, fluid physical properties, interlayer distribution, and development mode according to the actual reservoir physical properties. Through the visualization of experimental equipment, the bottom water reservoir is visually stimulated. The displacement and sweep law of natural water drive and artificial water injection in bottom water reservoir with or without an interlayer, different viscosity, and different well spacing is analyzed. The following conclusions are obtained: (1) For reservoirs with a viscosity of 150 cp. The recovery factor after water injection is slightly higher than before water injection. However, the recovery factor is lower than that without injection production. The reason is that the increment of injection conversion is limited to reduce one production well after injection conversion. (2) For reservoirs with a viscosity of 30 cp. The recovery factor after injection is 39.8%, which is slightly higher than 38.9% without injection. (3) For reservoirs with a viscosity of 150 cp. In the case of the interlayer. The recovery factor after injection is 30.7%, which is significantly higher than 24.8% without injection. (4) After the well spacing of the low-viscosity reservoir is reduced, the recovery factor reaches 46.1%, which is higher than 38.9% of the non-infill scheme. After the infill well in a low-viscosity reservoir is transferred to injection, the recovery factor is 45.6%, which has little change compared with non-injection, and most of the cumulative production fluid is water. The feasibility and effect of water flooding in a strong bottom water reservoir are demonstrated. This study provides the basis for the proposal of production well injection conversion and the adjustment of production parameters in the highest water cut stage of a big bottom water reservoir.

Field Performances, Effective Times, and Economic Assessments of Polymer Gel Treatments in Controlling Excessive Water Production From Mature Oil Fields

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Munqith Aldhaheri ◽  
Mingzhen Wei ◽  
Ali Alhuraishawy ◽  
Baojun Bai
Keyword(s):  
Fractured Reservoirs ◽  
Descriptive Analysis ◽  
Naturally Fractured Reservoirs ◽  
Oil Fields ◽  
Water Production ◽  
Polymer Gel ◽  
Rock Formations ◽  
Water Cut ◽  
Matrix Rock ◽  
Excessive Water

Abstract Polymer bulk gels have been widely applied to mitigate excessive water production from mature oil fields by correcting the reservoir permeability heterogeneity. This paper reviews water responses, effective times, and economic assessments of injection-well gel treatments based on 61 field projects. Eight parameters were evaluated per the reservoir type using the descriptive analysis, stacked histograms, and scatterplots. Results show that water production generally continues to increase after the treatment for undeveloped conformance problems. Contrarily, it typically decreases after the reactive gel treatments target developed conformance issues. For the developed problems, gel treatments do not always mitigate the water production where the water cut may stabilize or increase by 17% in 22% of instances. In addition, they often do reduce water production but not dramatically to really low levels where the water cut stays above 70% and reduces by only 10% in most cases. Gel treatments are economically appraised based only on the oil production response, and both water responses (injection and production) are not considered in the evaluation. They have a typical payout time of 9.2 months, cost of incremental oil barrel of 2 $/barrel, and effective time of 1.9 years. In addition, they have better water responses and economics in carbonates than in sandstones and in unconsolidated and naturally fractured reservoirs than in matrix-rock formations. The current review strongly warns reservoir engineers that gel treatments are not superior in alleviating the water production and candidates should be nominated based on this fact to achieve favorable economics and avoid treatment failures.

Determination and Implication of Ultimate Water Cut in Well-Spacing Design for Developed Reservoirs With Water Coning

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Samir Prasun ◽  
A. K. Wojtanowicz
Keyword(s):  
Production Rate ◽  
Reservoir Properties ◽  
Flow Distortion ◽  
Practical Applications ◽  
Rate Dependent ◽  
Well Spacing ◽  
Water Coning ◽  
Simplifying Assumptions ◽  
Water Cut ◽  
New Formula

Theoretically, ultimate water-cut (WCult) defines stabilized well's oil and water production rates for uncontained oil pay underlain with water. However, in a real multiwell reservoir, the well's drainage area is contained by a no-flow boundary (NFB) that would control water coning, so the WCult concept should be qualified and related to the well-spacing size. Also, the presently used WCult formula derives from several simplifying assumptions, so its validity needs to be verified. The study shows that in multiwell bottom-water reservoirs, the production water-cut would never stabilize (after initial rapid increase) but would continue increasing at slow rate dependent on the production rate and well-spacing size. At each production rate, there is a minimum well-spacing size above which water-cut becomes practically constant at the value defined here as pseudoWCult. A new formula—developed in this study—correlates the minimum well-spacing with reservoir properties. Further, formula for pseudoWCult is derived by considering radial flow distortion effects in the oil and water zones. It is found that for well-spacing larger than the minimum well-spacing, the two effects-when combined-do not change the water-cut value. Thus, in practical applications, for sufficiently large well-spacing, the pseudoWCult values can be computed from the presently used WCult formula. The pseudoWCult concept has potential practical use in well-spacing design for ultimate recovery determined by the water cut economic limit, WCec. When the water-cut economic margin (WCec–WCult) is large, well-spacing has little effect on the ultimate recovery, so large well-spacing could be designed. However, when the water-cut economic margin is small, reservoir development decision should consider increase of final recovery by reducing well-spacing below the minimum well-spacing.

Evaluating Water Coning Control for Horizontal Well in Bottom-Water Sandstone Reservoirs by Numerical Method

2012 ◽  
Vol 524-527 ◽  
pp. 292-296
Author(s):  
Rong Wang ◽  
Kui Zhang ◽  
Yong Gang Duan ◽  
Ting Kuan Cao
Keyword(s):  
Horizontal Well ◽  
Bottom Water ◽  
Negative Impact ◽  
Oil Production ◽  
High Water ◽  
Control Effect ◽  
Water Coning ◽  
Sandstone Reservoirs ◽  
High Water Cut Stage ◽  
Water Cut

Horizontal well is the main technology to develop bottom-water sandstone reservoirs. Water coning has a significant influence on development effect, and shut-in coning control is one of coning suppression methods. Based on the geological model of a given oilfield, this paper has made an evaluation of water coning control by numerical simulation. It can be concluded that the method of shut-in coning control is effective for low water cut wells. When shutting in, the lower the water cut is, the greater decline extent of water cut can be obtained and the higher cumulative oil production can be achieved after well reopening. The longer the close time is, the better water coning control effect can be acquired, however it will affect oil production undoubtly. When horizontal well enters into high water cut stage, shut-in coning control not only has almost no effect, but also has a negative impact on the normal oil production.

Sign in / Sign up

Export Citation Format

Share Document