Comparison of Type Well Generation Methods for Unconventional Reservoirs

SPE Reservoir Evaluation & Engineering ◽

10.2118/205022-pa ◽

2021 ◽

pp. 1-18

Author(s):

Oubaida Taji ◽

Doruk Alp

Keyword(s):

Field Data ◽

Production Performance ◽

Unconventional Reservoirs ◽

Real Field ◽

Shale Oil ◽

Decline Curve ◽

Shale Oil Reservoirs ◽

The Impact ◽

Ultralow Permeability ◽

Mc Method

Summary Due to ultralow permeability, there is practically no pressure interference between wells producing from tight oil (≈0.1 md average permeability) and shale oil reservoirs (∼0.001 md average permeability). This renders type well methodology as a commonly used tool for forecasting production performance of these “unconventionals.” Several authors proposed different methods for constructing type wells for unconventional reservoirs, but none compared them. In this study, we compare three of the most common types of well generation methods. In the absence of real field data, individual production histories for wells are established by picking Arps decline curve parameters qi, b, and Di, which govern a well’s production performance, from respective distributions of these parameters. Next, we compare type wells constructed using the Monte Carlo (MC) method, final cumulative (FC) method, and time slice (TS) method. Moreover, we study the impact of a possible linear correlation (also linear C) between b and Di (comparable to field observations) on MC, FC, and TS type wells. We also study the effect of well count, and Dmin value, which is the 4th parameter introduced with modified Arps equation for unconventionals. In this paper, we show that type wells generated with TS and FC methods have almost the same behavior, whereas the MC method is affected the most by stochastic experimentation, well count, and Dmin.

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Experimental Study on the Impact of Supercritical CO2 Soak Pre-Treatment on Re-Fracturing of Shale Oil Reservoirs

10.2118/202421-ms ◽

2020 ◽

Author(s):

Jiaping Tao ◽

Siwei Meng ◽

Gang Cao ◽

Yang Gao ◽

He Liu

Keyword(s):

Experimental Study ◽

Supercritical Co2 ◽

Oil Reservoirs ◽

Shale Oil ◽

Pre Treatment ◽

Shale Oil Reservoirs ◽

The Impact

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Household quarantine of second degree contacts is an effective non-pharmaceutical intervention to prevent tertiary cases in the current SARS-CoV pandemic

BMC Infectious Diseases ◽

10.1186/s12879-021-06818-w ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Josef A. I. Weigl ◽

Anna-Katharina Feddersen ◽

Mona Stern

Keyword(s):

Cohort Study ◽

Retrospective Cohort ◽

Field Data ◽

Health Department ◽

Real Field ◽

Northern Germany ◽

Limited Efficacy ◽

County Health Department ◽

The Impact ◽

Second Degree

Abstract Background Given the characteristics of SARS-CoV2 with regard to transmission before the onset of symptoms and varying manifestation indices according to age, isolation and quarantine have limited efficacy in the current pandemic. Household quarantine in second degree contacts (Hh-Q2°) outside the case household has so far only been addressed by modellers. In the literature there is no publication based on field data. Methods In a retrospective cohort study on real field data from a county health department (CHD), all PCR-confirmed cases and related contact persons put into quarantine were analysed. Hh-Q2° was used in our CHD from the onset of the pandemic. Results From 9 March to 8 December 2020, 353 PCR-confirmed cases were registered in the CHD Ploen, Northern Germany: 225 (63.7%) primary, 107 (30.3%) secondary and 21 (5.9%) tertiary cases. The 107 secondary cases resulted out of 470 (22.8%) close or 1°contacts and 21 tertiary cases out of 179 (11.7%) indirect or 2°contacts put into quarantine. The efficacy of Hh-Q2° was 51.5% (11.7%/22.8%) of that of quarantine in 1°contacts; 16.4% of all converted cases in quarantined persons were ascertained by Hh-Q2°. One in ten 1°contacts in households with tertiary cases remained asymptomatic. Conclusion The impact of Hh-Q2° in preventing further spread of SARS-CoV2 was considerable. With half the conversion rate in 2°contacts compared to 1°contacts, the efficacy of Hh-Q2° is substantial. Hh-Q2° should definitely be used routinely to control the spread of SARS-CoV2 more efficiently and national authorities should include it in their guidelines.

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Household quarantine of second degree contacts is an effective non-pharmaceutical intervention to prevent tertiary cases in the current SARS-CoV pandemic

10.21203/rs.3.rs-900696/v1 ◽

2021 ◽

Author(s):

Josef A. I. Weigl ◽

Anna-Katharina Feddersen ◽

Mona Stern

Keyword(s):

Cohort Study ◽

Retrospective Cohort ◽

Field Data ◽

Health Department ◽

Real Field ◽

Northern Germany ◽

Limited Efficacy ◽

County Health Department ◽

The Impact ◽

Second Degree

Abstract Background Given the characteristics of SARS-CoV2 with regard to transmission before the onset of symptoms and varying manifestation indices according to age, isolation and quarantine have limited efficacy in the current pandemic. Household quarantine in second degree contacts (Hh-Q2°) outside the case household has so far only been addressed by modellers. In the literature there is no publication based on field data. Methods In a retrospective cohort study on real field data from a county health department (CHD), all PCR-confirmed cases and related contact persons put into quarantine were analysed. Hh-Q2° was used in our CHD from the onset of the pandemic. Results From 9 March to 8 December 2020, 353 PCR-confirmed cases were registered in the CHD Ploen, Northern Germany: 225 (63.7%) primary, 107 (30.3%) secondary and 21 (5.9%) tertiary cases. The 107 secondary cases resulted out of 470 (22.8%) close or 1°contacts and 21 tertiary cases out of 179 (11.7%) indirect or 2°contacts put into quarantine. The efficacy of Hh-Q2° was 51.5% (11.7%/22.8%) of that of quarantine in 1°contacts; 16.4% of all converted cases in quarantined persons were ascertained by Hh-Q2°. One in ten 1°contacts in households with tertiary cases remained asymptomatic. Conclusion The impact of Hh-Q2° in preventing further spread of SARS-CoV2 was considerable. With 51% of the conversion rate in 2°contacts compared to 1°contacts, the efficacy of Hh-Q2° is substantial. Hh-Q2° should definitely be used routinely to control the spread of SARS-CoV2 more efficiently and national authorities should include it in their guidelines.

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Well Completion Optimization in Unconventional Reservoirs Using Machine Learning Methods

10.2118/206241-ms ◽

2021 ◽

Author(s):

Sohrat Baki ◽

Cenk Temizel ◽

Serkan Dursun

Keyword(s):

Machine Learning ◽

Predictive Models ◽

Mapping Function ◽

Volume Effect ◽

Production Performance ◽

Unconventional Reservoirs ◽

Support Vector ◽

Feature Engineering ◽

Well Completion ◽

The Impact

Abstract Unconventional reservoirs, mainly shale oil and natural gas, will continue to significantly help meet the ever-growing energy demands of global markets. Being complex in nature and having ultra-tight producing zones, unconventionals depends on effective well completion and stimulation treatments in order to be successful and economical. Within the last decade, thousands of unconventional wells have been drilled, completed and produced in North America. The scope of this work is exploring the primary impact of completion parameters such as lateral length, frac type, number of stages, proppant and fluid volume effect on the production performance of the wells in unconventional fields. The key attributes in completion, stimulation, and production for the wells were considered in machine learning workflow for building predictive models. Predictive models based on Neural Networks, Support Vector Machines or Decision Tree Based ensemble models, serves as mapping function from completion parameters to production in each well in the field. The completion parameters were analyzed in the workflow with respect to feature engineering and interpretation. This analysis resulted in key performance indicators for the region. Then the optimum values for the best production performing completions were identified for each well. Predictive models in the workflow were analyzed in accuracy and best model is used to understand the impact of completion parameters on the production rates. This study outlines an overall machine learning workflow, from feature engineering to interpretation of the machine learning models to quantify the effects of completion parameters on the production rate of the wells in unconventional fields

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Closing the Gap in Characterizing the Parent Child Effect for Unconventional Reservoirs - A Case of Study in Vaca Muerta Shale Formation

10.2118/206001-ms ◽

2021 ◽

Author(s):

Alejandro Lerza ◽

Sergio Cuervo ◽

Sahil Malhotra

Keyword(s):

Hydraulic Fracture ◽

Production Performance ◽

Drainage Area ◽

Real Field ◽

Well Spacing ◽

Fracture Development ◽

Vaca Muerta ◽

Pressure Depletion ◽

The Impact ◽

Parent Child

Abstract In Shale and Tight, the term "Parent-Child effect" refers to the impact the depleted area and corresponding stress changes originated by the production of a previously drilled well, the "parent", has over the generated hydraulic fracture geometry, conforming initial drainage area and consequent production performance of a new neighbor well, called "child". Such effect might be considered analogous to the no flow boundary created when the drainage areas of two wells meet at a certain distance from them in conventional reservoirs; but, unconventional developments exhibit higher exposure to a more impactful version of this phenomena, given their characteristic tighter well spacing and the effect pressure depletion of the nearby area by the neighbor well has over the child well's hydraulic fracture development. Due to the importance the Parent-Child effect has for unconventional developments, this study aims first to generally characterize this effect and then quantify its expected specific project impact based on real field data from the Vaca Muerta formation. To do so, we developed a methodology where fracture and reservoir simulation were applied for calibrating a base model using field observed data such as microseismic, tracers, daily production data and well head pressure measurements. The calibrated model was then coupled with a geomechanical reservoir simulator and used to predict pressure and stress tensor profiles across different depletion times. On these different resulting scenarios, child wells were hydraulically fractured with varying well spacing and completion designs. Finally, the Expected Ultimate Recovery (EUR) impact versus well spacing and the parent´s production time were built for different child´s completion design alternatives, analyzed and contrasted against previously field observed data. Results obtained from the characterization work suggests the parent child effect is generated by a combination of initial drainage area changes and stress magnitude and direction changes, which are both dependent of the pressure depletion from the parent well. Furthermore, the results show how the well spacing and parent's production timing, as well as parent's and child's completion design, significantly affect the magnitude of the expected parent child effect impact over the child's EUR.

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Effect of Fracture Characteristics on Behavior of Fractured Shale-Oil Reservoirs by Cyclic Gas Injection

SPE Reservoir Evaluation & Engineering ◽

10.2118/168880-pa ◽

2016 ◽

Vol 19 (02) ◽

pp. 350-355 ◽

Cited By ~ 15

Author(s):

T.. Wan ◽

J. J. Sheng ◽

M. Y. Soliman ◽

Y.. Zhang

Keyword(s):

Oil Recovery ◽

Gas Injection ◽

Fracture Network ◽

Production Performance ◽

Oil Reservoirs ◽

Shale Oil ◽

Well Production ◽

The Matrix ◽

Stress Dependent ◽

Shale Oil Reservoirs

Summary The current technique to produce shale oil is to use horizontal wells with multistage stimulation. However, the primary oil-recovery factor is only a few percent. The low oil recovery and abundance of shale reservoirs provide a huge potential for enhanced oil-recovery (EOR) process. Well productivity in shale oil-and-gas reservoirs primarily depends on the size of fracture network and the stimulated reservoir volume (SRV) that provides highly conductive conduits to communicate the matrix with the wellbore. The fracture complexity is critical to the well-production performance, and it also provides an avenue for injected fluids to displace the trapped oil. However, the disadvantage of gasflooding in fractured reservoirs is that injected fluids may break through to production wells by means of the fracture network. Therefore, a preferred method is to use cyclic gas injection to overcome this problem. In this paper, we use a numerical-simulation approach to evaluate the EOR potential in fractured shale-oil reservoirs by cyclic gas injection. Simulation results indicate that the stimulated fracture network contributes significantly to the well productivity by means of its large contact area with the matrix, which prominently enhances the macroscopic sweep efficiency in secondary cyclic gas injection. In our previous simulation work, the EOR potential was evaluated in hydraulic planar-traverse fractures without considering the propagation of a natural-fracture network. In this paper, we examine the effect of fracture networks on shale oilwell secondary-production performance. The impact of fracture spacing and stress-dependent fracture conductivity on the ultimate oil recovery is investigated. The results presented in this paper demonstrate that cyclic gas injection has EOR potential in shale-oil reservoirs. This paper focuses on evaluating the effect of fracture spacing, the size of the fracture network, fracture connectivity (uniform and nonuniform), and stress-dependent fracture-network conductivity on well-production performance of shale-oil reservoirs by secondary cyclic gas injection.

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An equivalent method to assess the production performance of horizontal wells with complicated hydraulic fracture network in shale oil reservoirs

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2019.102975 ◽

2019 ◽

Vol 71 ◽

pp. 102975 ◽

Cited By ~ 1

Author(s):

Yan Dong ◽

Peichao Li ◽

Wei Tian ◽

Yuxi Xian ◽

Detang Lu

Keyword(s):

Hydraulic Fracture ◽

Horizontal Wells ◽

Fracture Network ◽

Production Performance ◽

Oil Reservoirs ◽

Shale Oil ◽

Hydraulic Fracture Network ◽

Shale Oil Reservoirs ◽

Equivalent Method

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Household Quarantine of Second Degree Contacts Is an Effective Non- Pharmaceutical Intervention to Prevent Tertiary Cases in the Current Pandemic

10.21203/rs.3.rs-318558/v1 ◽

2021 ◽

Author(s):

Josef A. I. Weigl ◽

Anna-Katharina Feddersen ◽

Mona Stern

Keyword(s):

Cohort Study ◽

Retrospective Cohort ◽

Field Data ◽

Health Department ◽

Real Field ◽

Northern Germany ◽

Limited Efficacy ◽

County Health Department ◽

The Impact ◽

Second Degree

Abstract Background: Given the characteristics of SARS-CoV2 in regard to transmission before the onset of symptoms and varying manifestation indices according to age, isolation and quarantine have limited efficacy in the current pandemic. Household quarantine in second degree contacts (Hh-Q2°) outside the case household was so far only addressed by modellers. There is no publication based on field data in the literature.Methods: In a retrospective cohort study on real field data from a county health department (CHD), all PCR-confirmed cases and related contact persons put into quarantine were analysed. Hh-Q2° was used in our CHD from the beginning of the pandemic.Results: From 9 March to 8 December 2020, 353 PCR-confirmed cases were registered in the CHD Ploen, Northern Germany: 225 (63.7%) primary, 107 (30.3%) secondary and 21 (5.9%) tertiary cases. The 107 secondary cases resulted out of 470 (22.8%) close or 1°contacts and 21 tertiary cases out of 179 (11.7%) indirect or 2°contacts put into quarantine. The efficacy of Hh-Q2° was 51.5% (11.7%/22.8%) of the efficacy of quarantine in 1°contacts; 16.4% of all converted cases in quarantined persons were ascertained by Hh-Q2°. One in ten 1°contacts in households with tertiary cases remained asymptomatic.Conclusion: The impact of Hh-Q2° in preventing further spread of SARS-CoV2 was considerable. With half the conversion rate in 2°contacts in comparison to 1°contacts, the efficacy of Hh-Q2° is substantial. Hh-Q2° should urgently be used routinely to control the spread of SARS-CoV2 more efficiently and national authorities should include it in their guidelines.

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