A Gravity Drainage Model for the Steam-Soak Process

1970 ◽  
Vol 10 (02) ◽  
pp. 119-126 ◽  
Author(s):  
C.H. Kuo ◽  
S.A. Shain ◽  
D.M. Phocas
Keyword(s):  
Temperature Distribution ◽  
Field Experience ◽  
Oil Production ◽  
Steam Injection ◽  
Production Performance ◽  
Gravity Drainage ◽  
Long Term Effects ◽  
Well Spacing ◽  
Number Of Cycles ◽  
Hot Zone

Abstract This paper deals with production performance for the steam-soak process, as applied to a reservoir where oil is produced by gravity drainage. It is assumed that the steamflooded zone is maintained at a fixed constant temperature and that a portion of the injected heat is transported into the cool zone by radial conduction. On the basis of these assumptions a mathematical model of the production performance has been constructed. The continuity performance has been constructed. The continuity equation is solved by a finite difference method to obtain the distribution of The height of free-oil surface. Then the flow rate and the cumulative oil production are calculated production are calculatedThe results of this study indicate that a large portion of the oil adjacent to the hot zone flows portion of the oil adjacent to the hot zone flows radially toward the production well in the early life. This occurs despite the fact that the formation near the outer boundary remains fairly cold. A high ultimate recovery of oil is predicted for repeated soaks for the case of a thick reservoir containing very viscous oil. The largest improvement in cumulative production from the steam-soak process over primary production is achieved when the hot-zone radius is less than or equal to one-quarter of the outer drainage radius. The further acceleration of oil production is very little for larger hot-zone radii. The time required to achieve a certain cumulative production is found to be cut more than one-half by production is found to be cut more than one-half by halving the well spacing. The selection of a close well spacing is suggested by this result. Introduction The steam-soak process has been a successful method of recovering very viscous oil from an underground reservoir. It involves injection of steam into. an oil-bearing formation for a certain period of time. The well is then closed in for a period of time. The well is then closed in for a short time, after which it is opened for oil production. These steam-injection and oil-production production. These steam-injection and oil-production processes are repeated for a number of cycles until processes are repeated for a number of cycles until the economic limit is reached. Because of the relatively short history of the steam-soak recovery process, field experience alone does not provide process, field experience alone does not provide enough information for estimation of long-term effects. These effects will influence the design of a field steam-soak operation. Therefore, it is desirable to supplement field experience with model studies. For example, a theoretical analysis of steam stimulation has been given by Martin. This paper deals with the production performance of a reservoir in which gravity drainage is the dominant production mechanism. In a previous study, Towson and Boberg predicted gravity drainage production rates utilizing the semisteady-state equation developed by Matthews and Lefkovits. Their predictions were based on the assumption that the zone not flooded by steam was maintained at the original formation temperature and the average temperature in the steamflooded zone varied with time as calculated from an energy balance. On the other hand, Seba and Perry assumed that the formation outside the steamflooded zone was heated to a uniform temperature while the temperature in the flooded region remained constant. They considered that, within the flooded zone, a rate equation obtained by Muskat for an infinite reservoir was applicable. Outside the flooded zone, the Matthews-Lefkovits equation was employed. The influence of temperature, and thus viscosity, on the fluid flow at larger distances from the producing well is important when considering long-term effects. Therefore, a more appropriate temperature distribution than is used in the previously referenced studies is required when previously referenced studies is required when estimating future production rates. The present work aims at combining a temperature distribution, which varies continuously in the part of the reservoir that is being heated by conduction from the hot zone, with a model of the fluid flow. With the temperature distribution specified, the continuity equation will be solved by finite difference methods to obtain the height of the free-oil surface as a function of time and radial distance. The cumulative oil produced can then be predicted. predicted. JPT P. 119

Numerical Simulation of Thermal Solvent Replacing Steam under Steam Assisted Gravity Drainage SAGD Process

2010 ◽  
Author(s):  
Weiqiang Li ◽  
Daulat D. Mamora
Keyword(s):  
High Temperature ◽  
Oil Recovery ◽  
Oil Sands ◽  
Steam Injection ◽  
Thermal Recovery ◽  
Production Performance ◽  
Gravity Drainage ◽  
Steam Assisted Gravity Drainage ◽  
Recovery Technique ◽  
Simulation Results

Abstract Steam Assisted Gravity Drainage (SAGD) is one successful thermal recovery technique applied in the Athabasca oil sands in Canada to produce the very viscous bitumen. Water for SAGD is limited in supply and expensive to treat and to generate steam. Consequently, we conducted a study into injecting high-temperature solvent instead of steam to recover Athabasca oil. In this study, hexane (C6) coinjection at condensing condition is simulated using CMG STARS to analyze the drainage mechanism inside the vapor-solvent chamber. The production performance is compared with an equivalent steam injection case based on the same Athabasca reservoir condition. Simulation results show that C6 is vaporized and transported into the vapor-solvent chamber. At the condensing condition, high temperature C6 reduces the viscosity of the bitumen more efficiently than steam and can displace out all the original oil. The oil production rate with C6 injection is about 1.5 to 2 times that of steam injection with oil recovery factor of about 100% oil initially-in-place. Most of the injected C6 can be recycled from the reservoir and from the produced oil, thus significantly reduce the solvent cost. Results of our study indicate that high-temperature solvent injection appears feasible although further technical and economic evaluation of the process is required.

scholarly journals A steam rising model of steam-assisted gravity drainage production for heavy oil reservoirs

2019 ◽  
Vol 38 (4) ◽  
pp. 801-818
Author(s):  
Ren-Shi Nie ◽  
Yi-Min Wang ◽  
Yi-Li Kang ◽  
Yong-Lu Jia
Keyword(s):  
Production Rate ◽  
Horizontal Well ◽  
Oil Production ◽  
Steam Injection ◽  
Injection Rate ◽  
Gravity Drainage ◽  
Model Parameters ◽  
Steam Quality ◽  
Steam Chamber ◽  
Steam Assisted Gravity Drainage

The steam chamber rising process is an essential feature of steam-assisted gravity drainage. The development of a steam chamber and its production capabilities have been the focus of various studies. In this paper, a new analytical model is proposed that mimics the steam chamber development and predicts the oil production rate during the steam chamber rising stage. The steam chamber was assumed to have a circular geometry relative to a plane. The model includes determining the relation between the steam chamber development and the production capability. The daily oil production, steam oil ratio, and rising height of the steam chamber curves influenced by different model parameters were drawn. In addition, the curve sensitivities to different model parameters were thoroughly considered. The findings are as follows: The daily oil production increases with the steam injection rate, the steam quality, and the degree of utilization of a horizontal well. In addition, the steam oil ratio decreases with the steam quality and the degree of utilization of a horizontal well. Finally, the rising height of the steam chamber increases with the steam injection rate and steam quality, but decreases with the horizontal well length. The steam chamber rising rate, the location of the steam chamber interface, the rising time, and the daily oil production at a certain steam injection rate were also predicted. An example application showed that the proposed model is able to predict the oil production rate and describe the steam chamber development during the steam chamber rising stage.

Expansion of Data Analytics for Optimizing Steamflood In Mukhaizna Heavy Oil Field

2021 ◽  
Author(s):  
Mohammed Al Asimi ◽  
Nasar Al Qasabi ◽  
Duc Le ◽  
Yuchen Zhang ◽  
Di Zhu ◽  
...  
Keyword(s):  
Heavy Oil ◽  
Data Analytics ◽  
Oil Production ◽  
Steam Injection ◽  
Lessons Learned ◽  
Oil Field ◽  
Production Performance ◽  
Optimization Process ◽  
Successful Implementation ◽  
Full Field

Abstract After successful implementation of data analytics for steamflood optimization at the Mukhaizna heavy oil field in Oman late 2018, Occidental expanded the project to two additional areas with a total of 626 wells in 2019, followed by full field coverage of more than 3,200 wells in 2020. In 2019, two separate low-fidelity proxy models were built to model the two pilot areas. The models were updated with more features to account for additional reservoir phenomena and a larger scope. On the proxy engine side, speed and robustness were improved, resulting in reduced CPU processing time and lower cost. Because of advancements in software programing and the pilots’ encouraging production performance, full-field coverage was accelerated so the model could support the efforts in optimizing steam injection during the 2020 OPEC+ production cut, not only to comply with allotted quotas, but also to allocate the resources optimally, especially the costly steam. Good improvements have been observed in overall steamflood performance, the models’ capabilities, and the optimization workflow. The steam/oil ratio has been reduced through the increase in oil production in both expanded study areas while keeping the total steam injection volume constant. Overall field steam utilization was improved both during the 2020 OPEC+ production cuts and during the production ramp-up stage afterward. With the continuous improvement in supporting tools and scripts, most of the steam optimization process steps were automated, from preparing, checking, and formatting input data to analyzing, validating, and visualizing the model outputs. Another result of these improvements was the development of a user-friendly web application to manage the model workflow efficiently. This web app greatly improved the process of case submittals, including data preparation and QC, running models (history matching and forecasting), as well as visualization of the entire workflow. In terms of optimization workflow, these improvements resulted in less time spent by the field optimization engineer in updating, refreshing, and generating new model recommendations. It also helped reduce the time spent by the reservoir management team (RMT) to test and validate the new ideas before field implementation. This paper will describe the improvements in the proxy model and the overall optimization process, show the observed oil production increases, and discuss the challenges faced and the lessons learned.

How to Space SAGD Well Pairs for Optimal Performance

2021 ◽  
Author(s):  
Zeinab Zargar ◽  
S. M. Farouq Ali
Keyword(s):  
Oil Recovery ◽  
Moving Boundary ◽  
Late Phase ◽  
Oil Production ◽  
Steam Injection ◽  
Injection Rate ◽  
Analytical Relation ◽  
Oil Sand ◽  
Steam Quality ◽  
Well Spacing

Abstract Steam-Assisted Gravity Drainage (SAGD) is a remarkably successful process for the tar sands (oil sands). Two closely spaced parallel horizontal wells, injector above the producer, form a SAGD well pair. Steam is injected to provide heat to the reservoir oil and mobilize it. The low viscosity oil drains down to the producer under the gravity effect. Parallel well pairs 1000 m long are utilized in the process, spaced 100 m apart horizontally almost in all projects. In this work, an analytical model for the SAGD process is introduced by coupling heat and fluid flow and constitutive equations. A moving boundary, counter-current flow approach is used for the steam chamber rise and subsequent sideways expansion. The model is unique because it assumes the steam injection rate is constant and it permits modeling of the late phase of SAGD when adjacent well pair interference occurs. This leads to a reduction in heat loss to the overburden and a decline in oil production rate. This study examines the question of optimal well pair spacing in relation to the formation thickness and in-place oil. The effect of other variables on SAGD performance is investigated. A case study was performed using Christina Lake oil sand properties to show how the project performance varies under different senerios involving well pair spacing, reservoir thickness, steam injection rate, and steam quality. Results show that, in evaluating a SAGD pad performance, as the spacing is increased, the cumulative oil production decreases, with a simultanous increase in the cumulative steam-oil ratio at the same steam injection rate. However, a smaller portion of injected heat is lost to the overburden. It is concluded that a smaller well spacing requires more wells to deplete the whole pad area. On the other hand, a larger pattern well spacing affects oil recovery and heat consumption. Different conclusions are derived for the same pattern well spacing value using a single well pair model and pattern well pair configuration. Results also show that SAGD well pair spacing can be increased with an increase in formation thickness. The computational procedure is simple and makes it possible to examine a series of options for well spacing for a given set of conditions. This study presents for the first time an analytical relation between SAGD pattern well pair spacing and oil recovery.

Inflow Performance of a Cyclic-Steam-Stimulated Horizontal Well Under the Influence of Gravity Drainage

SPE Journal ◽  
2011 ◽  
Vol 16 (03) ◽  
pp. 494-502 ◽  
Author(s):  
Z.. Wu ◽  
S.. Vasantharajan ◽  
M.. El-Mandouh ◽  
P.V.. V. Suryanarayana
Keyword(s):  
Heavy Oil ◽  
Horizontal Well ◽  
Oil Production ◽  
Steam Injection ◽  
Oil Field ◽  
Gravity Drainage ◽  
Attractive Alternative ◽  
Underlying Assumption ◽  
Heated Oil ◽  
Condensed Water

Summary In this paper, we present a new, semianalytical gravity-drainage model to predict the oil production of a cyclic-steam-stimulated horizontal well. The underlying assumption is that the cyclic steam injection creates a cylindrical steam chamber in the upper area of the well. Condensed water and heated oil in the chamber are driven by gravity and pressure drawdown toward the well. The heat loss during the soak period and during oil production is estimated under the assumption of vertical and radial conduction. The average temperature change in the chamber during the cycle is calculated using a semianalytical expression. Nonlinear, second-order ordinary differential equations are derived to describe the pressure distribution caused by the two-phase flow in the wellbore. A simple iteration scheme is proposed to solve these equations. The influx of heated oil and condensed water into the horizontal wellbore is calculated under the assumption of steady-state radial flow. The solution from the semianalytical formulation is compared against the results from a commercial thermal simulator for an example problem. It is shown that the model results are in good agreement with those obtained from reservoir simulation. Sensitivity studies for optimization of wellbore length, gravity drainage, bottomhole pressure, and steam-injection rate are conducted with the model. Results indicate that the proposed model can be used in the optimization of individual-well performance in cyclic-steam-injection heavy-oil development. The semianalytical thermal model presented in this work can offer an attractive alternative to numerical simulation for planning heavy-oil field development.

Waterflooding in Carbonate Reservoirs: Does the Salinity Matter?

2014 ◽  
Vol 17 (03) ◽  
pp. 304-313 ◽  
Author(s):  
A.M.. M. Shehata ◽  
M.B.. B. Alotaibi ◽  
H.A.. A. Nasr-El-Din
Keyword(s):  
Oil Recovery ◽  
Sudden Change ◽  
Oil Production ◽  
Deionized Water ◽  
Production Performance ◽  
Shallow Aquifer ◽  
Secondary Recovery ◽  
Tertiary Recovery ◽  
The Impact ◽  
Indiana Limestone

Summary Waterflooding has been used for decades as a secondary oil-recovery mode to support oil-reservoir pressure and to drive oil into producing wells. Recently, the tuning of the salinity of the injected water in sandstone reservoirs was used to enhance oil recovery at different injection modes. Several possible low-salinity-waterflooding mechanisms in sandstone formations were studied. Also, modified seawater was tested in chalk reservoirs as a tertiary recovery mode and consequently reduced the residual oil saturation (ROS). In carbonate formations, the effect of the ionic strength of the injected brine on oil recovery has remained questionable. In this paper, coreflood studies were conducted on Indiana limestone rock samples at 195°F. The main objective of this study was to investigate the impact of the salinity of the injected brine on the oil recovery during secondary and tertiary recovery modes. Various brines were tested including deionized water, shallow-aquifer water, seawater, and as diluted seawater. Also, ions (Na+, Ca2+, Mg2+, and SO42−) were particularly excluded from seawater to determine their individual impact on fluid/rock interactions and hence on oil recovery. Oil recovery, pressure drop across the core, and core-effluent samples were analyzed for each coreflood experiment. The oil recovery using seawater, as in the secondary recovery mode, was, on the average, 50% of original oil in place (OOIP). A sudden change in the salinity of the injected brine from seawater in the secondary recovery mode to deionized water in the tertiary mode or vice versa had a significant effect on the oil-production performance. A solution of 20% diluted seawater did not reduce the ROS in the tertiary recovery mode after the injection of seawater as a secondary recovery mode for the Indiana limestone reservoir. On the other hand, 50% diluted seawater showed a slight change in the oil production after the injection of seawater and deionized water slugs. The Ca2+, Mg2+, and SO42− ions play a key role in oil mobilization in limestone rocks. Changing the ion composition of the injected brine between the different slugs of secondary and tertiary recovery modes showed a measurable increase in the oil production.

Unlocking By-Passed Oil with Autonomous Inflow Control Devices Through an Integrated Approach

2021 ◽  
Author(s):  
Pawan Agrawal ◽  
Sharifa Yousif ◽  
Ahmed Shokry ◽  
Talha Saqib ◽  
Osama Keshtta ◽  
...  
Keyword(s):  
Continuous Production ◽  
Oil Production ◽  
Gas Production ◽  
Oil Field ◽  
Production Performance ◽  
Fluid Distribution ◽  
Flow Profile ◽  
Horizontal Drain ◽  
Control Devices

Abstract In a giant offshore UAE carbonate oil field, challenges related to advanced maturity, presence of a huge gas-cap and reservoir heterogeneities have impacted production performance. More than 30% of oil producers are closed due to gas front advance and this percentage is increasing with time. The viability of future developments is highly impacted by lower completion design and ways to limit gas breakthrough. Autonomous inflow-control devices (AICD's) are seen as a viable lower completion method to mitigate gas production while allowing oil production, but their effect on pressure drawdown must be carefully accounted for, in a context of particularly high export pressure. A first AICD completion was tested in 2020, after a careful selection amongst high-GOR wells and a diagnosis of underlying gas production mechanisms. The selected pilot is an open-hole horizontal drain closed due to high GOR. Its production profile was investigated through a baseline production log. Several AICD designs were simulated using a nodal analysis model to account for the export pressure. Reservoir simulation was used to evaluate the long-term performance of short-listed scenarios. The integrated process involved all disciplines, from geology, reservoir engineering, petrophysics, to petroleum and completion engineering. In the finally selected design, only the high-permeability heel part of the horizontal drain was covered by AICDs, whereas the rest was completed with pre-perforated liner intervals, separated with swell packers. It was considered that a balance between gas isolation and pressure draw-down reduction had to be found to ensure production viability for such pilot evaluation. Subsequent to the re-completion, the well could be produced at low GOR, and a second production log confirmed the effectiveness of AICDs in isolating free gas production, while enhancing healthy oil production from the deeper part of the drain. Continuous production monitoring, and other flow profile surveys, will complete the evaluation of AICD effectiveness and its adaptability to evolving pressure and fluid distribution within the reservoir. Several lessons will be learnt from this first AICD pilot, particularly related to the criticality of fully integrated subsurface understanding, evaluation, and completion design studies. The use of AICD technology appears promising for retrofit solutions in high-GOR inactive strings, prolonging well life and increasing reserves. Regarding newly drilled wells, dedicated efforts are underway to associate this technology with enhanced reservoir evaluation methods, allowing to directly design the lower completion based on diagnosed reservoir heterogeneities. Reduced export pressure and artificial lift will feature in future field development phases, and offer the flexibility to extend the use of AICD's. The current technology evaluation phases are however crucial in the definition of such technology deployments and the confirmation of their long-term viability.

Gravity Drainage System: Investigation and Field Development Using Geological Modelling and Reservoir Simulation

2021 ◽  
Author(s):  
Obinna Somadina Ezeaneche ◽  
Robinson Osita Madu ◽  
Ishioma Bridget Oshilike ◽  
Orrelo Jerry Athoja ◽  
Mike Obi Onyekonwu
Keyword(s):  
Reservoir Simulation ◽  
Structural Control ◽  
History Matching ◽  
Drainage System ◽  
Production Performance ◽  
Gravity Drainage ◽  
Base Case ◽  
Proper Understanding ◽  
Field Development ◽  
Reservoir Performance

Abstract Proper understanding of reservoir producing mechanism forms a backbone for optimal fluid recovery in any reservoir. Such an understanding is usually fostered by a detailed petrophysical evaluation, structural interpretation, geological description and modelling as well as production performance assessment prior to history matching and reservoir simulation. In this study, gravity drainage mechanism was identified as the primary force for production in reservoir X located in Niger Delta province and this required proper model calibration using variation of vertical anisotropic ratio based on identified facies as against a single value method which does not capture heterogeneity properly. Using structural maps generated from interpretation of seismic data, and other petrophysical parameters from available well logs and core data such as porosity, permeability and facies description based on environment of deposition, a geological model capturing the structural dips, facies distribution and well locations was built. Dynamic modeling was conducted on the base case model and also on the low and high case conceptual models to capture different structural dips of the reservoir. The result from history matching of the base case model reveals that variation of vertical anisotropic ratio (i.e. kv/kh) based on identified facies across the system is more effective in capturing heterogeneity than using a deterministic value that is more popular. In addition, gas segregated fastest in the high case model with the steepest dip compared to the base and low case models. An improved dynamic model saturation match was achieved in line with the geological description and the observed reservoir performance. Quick wins scenarios were identified and this led to an additional reserve yield of over 1MMSTB. Therefore, structural control, facies type, reservoir thickness and nature of oil volatility are key forces driving the gravity drainage mechanism.

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