Cyclic Steam Stimulation Research Articles

Assessment of artificial lift methods for a heavy oil field in Kuwait

This paper describes a systematic assessment of artificial lift (AL) methods for a heavy oil development in Kuwait. The main recovery strategies that were being considered for the development consisted of different sequencing of primary production, cyclic steam stimulation and steam flooding, with both vertical and horizontal wells.Initially, Kuwait Oil Company drilled five vertical wells in their heavy oil fields, as a precursor to the full field development planned in the coming years. These five wells represented the first major activity in the formation since the 1980s, when two cyclic steam stimulation pilot tests were conducted. The characteristics of the development and of the associated planned recovery strategies presented several AL challenges that needed to be assessed.This work consisted of an assessment of the strengths and weaknesses of various AL systems and a ranking of these systems according to well geometry, oil viscosity, targeted flow rate and the recovery method. The assessment and ranking were mainly based on vendor quoted capabilities, focused wellbore modelling and lessons learned from other heavy oil field cases around the world. While significant experience with rod pumps in cyclic steam stimulation exists in Canada, the lessons learned from that experience needed to be evaluated due to the differences with the Kuwait heavy oil development, such as the requirement to “easily” transition from primary to thermal production and the possible use of metallic stator progressing cavity pumps. This paper provides guidance to other developments around the world in regards to heavy oil AL selection and to how best to apply lessons learned from existing heavy oil developments.

An integrated model for productivity prediction of cyclic steam stimulation with horizontal well

AbstractAs the accurate productivity prediction of cyclic steam stimulation with horizontal well (CSSHW) is essential for its effective utilization in heavy oil reservoirs, a novel integrated model for predicting productivity ofCSSHWwas proposed in this paper. Firstly, governing equations to predict thermophysical parameters of injected steam in the horizontal well were established. On the basis, the heating model for radius of hot fluid zone and steam zone were derived respectively according to a more realistic temperature distribution of formation. Then, coupled with heating model, the productivity prediction model was established according to the principle of equivalent percolation resistance. Then, comparisons have been made among the new model results,CMG STARSresults, and measured data to verify its accuracy. Finally, after the new proposed model is validated, the effects of steam quality and injection rate on heating radius and oil production were analyzed in detail. The results indicate that the result of new model is in good agreement with that ofCMG STARSand measured data, verifying the correctness of the model. In addition, the radius of hot fluid zone and steam zone both decreases with horizontal well length because of the heat losses as the steam flows along the horizontal wellbore. Influential factor analysis shows that high steam quality and steam injection rate can improve heating radius and cumulative oil production.

Stable isotopes of clay minerals from autoclave tests of oil sands: Implications for clay formation during steaming of Alberta Clearwater oil sands

In an effort to evaluate mineral-water isotopic exchange during cyclic steam stimulation (CSS), solutions and <2 μm berthierine-dominated solids from the Clearwater Formation oil sands of Alberta, Canada were analyzed for stable isotope compositions before and after reaction in autoclaves for 1008 h at 250 °C. There was no significant change in solution δ18O and δ2H, which is consistent with the high water/mineral ratio used in the experiments. The solids showed a marked decrease in both δ18O and δ2H following the experiments. Pre-run solids have δ18O of +9.5 to +12.9‰ and δ2H of −114 to −113‰, whereas post-run solids have δ18O of −4.7 to +2.1‰ and δ2H of −147 to −128‰. Neither oxygen- nor hydrogen-isotope equilibrium was established between the solids and the solutions. Calculation suggests that oxygen-isotope exchange (44–58%) was greater between the solids and the solutions than was the case for hydrogen isotopes (23–50%). We propose that this behaviour resulted from partial inheritance of the pre-run berthierine structure during formation of the post-run smectite, chlorite-smectite and chlorite. This process confounds the use of clay mineral stable isotope compositions as a temperature indicator of in situ steam/steam condensate interaction with oil-sands reservoirs. The results also suggest an additional mechanism by which new clay minerals can be formed during CSS-related, artificial diagenesis.

Technology Focus: Heavy Oil

Technology Focus I was asked to serve on the JPT Editorial Committee for another 3-year term and happily accepted the offer. In pre-paring for this month’s feature, I revisited my first Technology Focus writeup for the March 2016 issue. I concluded the piece by saying, “Before closing, I would like to bring your attention to two critical points as we experience one of the more severe economic downturns in the oil industry. First, research on technology for heavy-oil recovery must go on one way or another. … Second, cost-effective solutions should be sought and materialized immediately to sustain many ongoing heavy-oil (especially thermal) operations.” What has happened over the last 3 years in relation to these two issues I raised in March 2016? Here are some highlights of my observations. Heavy-oil recovery is a challenge mainly because of the high cost of investment and difficulties and uncertainties in operations; hence, the main issue is the reduction of cost per barrel of oil produced. This reduction to cost can be achieved either by recovery improvement or operational-/capital-expenditure (OPEX/CAPEX) reduction through optimization studies. Recovery improvement requires more research efforts and time-demanding technology development, but the cost reduction is less uncertain and the focus has been on both reduction methods, mainly CAPEX, during the low-oil-price term. OPEX constitutes a greater portion of the total cost than CAPEX. OPEX-reduction efforts have focused on the optimization of artificial lift in producing wells, steam delivery, and monitoring in injectors, as well as tackling problems such as emulsification, sand production, and asphaltene/wax precipitation. Solar steam is an option for OPEX reduction but is still a challenge because it requires high CAPEX and raises sustainability issues. Considering the development of new technologies for efficient recovery improvement, all agree that collaboration is a must, especially in carrying the research results to the field. Yet who (e.g., national oil companies, international oil companies, or service companies) will lead this action is still a question. Government involvement also should be part of this collaboration. Another necessary discussion point is the replacement of costly and environmentally risky steam operations. Nonsteam applications are showing promising results at the laboratory scale (e.g., solvents, electrical heating, and waterflooding with chemicals and nanomaterials), and methods to improve steam efficiency through chemical additives are yet to be tested at the field scale. The cost reduction per barrel of oil produced and the extension of sustainable production life by optimization have been two major areas of focus, but the investments in new technologies and recovery-improvement research have not received sufficient attention during the downturn. Recommended additional reading at nePetro: www.onepetro.org. SPE 189716 Shallow Horizontal-Well Cyclic Steam Stimulation in a Clastic Unconsolidated Unconventional Reservoir in Kuwait: A Case Study by Shaikha Al-Ballam, Kuwait Oil Company, et al. SPE 190111 Laboratory Tests Conducted To Perforate and Displace Viscous Oil From Saturated Formation Core To Help Optimize Steamflood Completion by Dennis J. Haggerty, Halliburton SPE 190770 Visualization of Heavy-Oil Mobilization by Associative Polymer by Tormod Skauge, Centre for Integrated Petroleum Research, et al.

Effect of bottom water on performance of cyclic superheated steam stimulation using a horizontal well

Horizontal well has been widely used for heavy-oil recovery in the petroleum industry. Besides, superheated steam has been proved effective in heavy-oil recovery by field practice. In this paper, a numerical model is established with the help of numerical simulator. The effect of bottom water on the productivity of cyclic superheated steam stimulation well has been studied. Some interesting findings show that: (a) the bottom water-channeling phenomenon becomes more severe when the horizontal well is approaching the bottom water. (b) The cyclic oil production fluctuates with periodic number when the horizontal well is close to the bottom water due to the fact that the injected water has an elastic push action on the bottom water. (c) A larger-bottom water size is able to supply a larger elastic energy. While the cyclic oil production of large-bottom water size for the first few cycles is smaller than that with a small-bottom water, it may be turned over for the last few cycles.

Application of Thermotropic Compositions for EOR with Cyclic-Steam Stimulation at Permian-Carboniferous Deposit of Usinsk Oilfield

Application of Thermotropic Compositions for EOR with Cyclic-Steam Stimulation at Permian-Carboniferous Deposit of Usinsk Oilfield

Experimental investigation and field pilot testing of air assisted cyclic steam stimulation technique for enhanced heavy oil recovery

Air assisted cyclic steam stimulation (AACSS) process is a novel technique for enhanced heavy oil recovery, which is efficient and economically attractive compared with other non-condensable gases and solvents injection-based techniques. In this study, the performance of AACSS process for an ultra heavy oil reservoir was investigated via laboratory experiments and field data analysis. The results indicate that air injection based on steam stimulation can effectively increase oil recovery in comparison with the conventional cyclic steam stimulation (CSS) process. The injected air can significantly increase and maintain the reservoir pressure, and reduce oil viscosity via flue gas dissolution and the thermal effect of low temperature oxidation (LTO) of the crude oil. The field pilot testing results of the AACSS technique in Liaohe Oilfield (Northeast China) demonstrate that AACSS can significantly increase oil production, prolong the effective production period of time, reduce water cut and the steam to oil ratio. A scoping economic study shows that the AACSS process can be more economically attractive than CSS process in terms of net present value. The AACSS technique has been effectively applied in mature heavy oil reservoirs developed by the conventional CSS, and it is also a feasible option to deep and offshore heavy oil reservoirs. [Received: January 6, 2017; Accepted: August 10, 2017]

Experimental investigation and field pilot testing of air assisted cyclic steam stimulation technique for enhanced heavy oil recovery

Experimental investigation and field pilot testing of air assisted cyclic steam stimulation technique for enhanced heavy oil recovery

Investigation on the Benefits of Steam Adsorption and Distribution during Cyclic Steam Injection to Improve Oil Recovery - FNE Case Study, Sudan

One of the main types of Enhanced Oil Recovery (EOR) methods is thermal stimulation method which is an increasingly common method of extracting heavy oil. there are different forms of the technology of thermal method Cyclic steam stimulation, Steam flooding and In-situ combustion “Fire flooding” are commonly applied to oil reservoirs, which are relatively shallow very viscous oil at the reservoir temperature, the most widely used steam injection methods for heavy oil recovery is Cyclic Steam Stimulation “steam soak or huff and puff” method. Most of commingle thermal wells has a problem in steam intensity distribution among the layers, which will lead to inconsistency in steam adsorption and some layers would adsorb more than double of the designed steam injected volume. This phenomenon will lead to low productivity and negatively impact the distribution of water cut in the different layers. Steam adsorption and distribution represent one of the main challenges of heavy oil production from Sudanese oil fields, very limited studies have been conducted in this field in Sudan oil fields, and this study is focused on addressing this challenge to maximize recover factor from each well and each field. In this paper the challenge facing Bentiu reservoir in Fula North East (FNE) located in heavy oil zone with target of production around 85% of the total reserves will be highlighted. The field has shallow depth ranging between 520m and 700m and low pressure gradient 1.09 psi/m, and with reservoir temperature around 44 o C. The study covers an investigation on the benefits of steam adsorption to enhance the oil recovery focusing on the distribution of the steam inside the layers, also cover the analyzing and reviewing the actual steam intensity distribution among each layer in the two wells that are later compared with the designed ones. In a later stage, we designed a pilot model that has been designed using advanced thermal EOR Simulator to understand the effect of commingle injection and production (Steam adsorption and distribution) using data from single layers. An optimum steam injection protocol that will maximize the recovery factor from these oil zones has been designed and the results show that the injection rate has significant effect in steam distribution. Keywords: Cyclic Steam Stimulation, Enhanced Oil Recovery (EOR), Steam-Assisted Gravity Drainage (SAGD), Hot water flooding and In situ combustion,

Incorporation of Hydroxyethylcellulose-Functionalized Halloysite as a Means of Decreasing the Thermal Conductivity of Oilwell Cement

The significant heat loss and severe thermal fluctuations inherent in steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) impose considerable constraints on well cementing. In order to obtain better energy efficiency and mechanical robustness, there is considerable interest in the development of low-thermal-conductivity cement that can provide a combination of enhanced thermal insulation and mechanical resilience upon thermal cycling. However, the current palette of thermal cements is exceedingly sparse. In this article, we illustrate a method for decreasing the thermal conductivity of cement by inclusion of hydroxyethylcellulose-functionalized halloysite nanotubes. Halloysite/hydroxyethylcellulose inclusions offer an abundance of disparate interfaces and void space that can effectively scatter phonons, thereby bringing about a pronounced reduction of thermal conductivity. The microstructure of the nanocomposite cementitious matrix is strongly modified even as the compositional profile remains essentially unaltered. Modified cement nanocomposites incorporating halloysite nanotubes along with hydroxyethylcellulose in a 8:1 ratio with an overall loading of 2 wt.% exhibit the lowest measured thermal conductivity of 0.212 ± 0.003 W/m.K, which is substantially reduced from the thermal conductivity of unmodified cement (1.252 W/m.K). The ability to substantially decrease thermal conductivity without deleterious modification of mechanical properties through alteration of microstructure, inclusion of encapsulated void spaces, and introduction of multiple phonon-scattering interfaces suggests an entirely new approach to oilwell cementing based on the design of tailored nanocomposites.

Investigation of hot-water flooding after steam injection to improve oil recovery in thin heavy-oil reservoir

Cyclic steam stimulation (CSS) is one of the popular methods to recovery heavy oil reserves that play an important role in supplying the energy consumption over the world. To solve the problems during the late CSS, we perform the feasibility study of hot-water flooding (HWF) after CSS with laboratory experiments and numerical simulation. The experimental results revealed the optimized water temperature to conduct HWF is 120 °C and the correct moment to convert is when the oil recovery of steam injection reaches 20%. Based on the geological properties of Jinlou oilfield in China, a series of numerical simulations were run to analyze the influence of several sensitive factors. It is necessary to transform development method because there are large quantities of remaining oil assembling at the inter-well region during the late stage of CSS and this after analyzing the oil saturation, reservoir temperature and oil viscosity distribution. The effect of HWF in reverse-rhythm and compound-rhythm reservoir is satisfactory, but is poor in positive-rhythm reservoir. It is suitable to reservoirs with thickness lower than 5 m and permeability variation coefficient less than 0.3. This study can provide a reference for enhanced oil recovery for thin heavy oil reservoirs after steam injection.

Mechanistic simulation study of air injection assisted cyclic steam stimulation through horizontal wells for ultra heavy oil reservoirs

Air injection assisted cyclic steam stimulation (CSS) through horizontal wells is a new technique for the exploitation of ultra heavy oil reservoirs, which has an advantage over other gas or solvent injection processes from the economic point of view. Different from in-situ combustion (ISC) process, the dominating chemical reactions occurring underground in air injection assisted CSS process are low temperature oxidation (LTO) reactions, and owing to the complicated LTO reaction mechanism, this process is still not clearly understood. Therefore, an indepth learning of this process will be of great benefit to its field application and specific project design. In this study, a comprehensive numerical simulation model was established, which accounted for the LTO reactions of different oil components in terms of SARA fractions, as well as permeability reduction induced by coke deposition. A series of simulations were then performed to explore the production performance and elucidate the impacts of various factors. The simulation results demonstrate that air injection assisted CSS using horizontal wells can enhance ultra heavy oil recovery and reduce cSOR in comparison with steam injection alone, which can be attributed to the synergistic effect of steam and air coinjection. Injection of air along with steam can have the same effect as the initial solution gas in reservoir, and the potential of air injection assisted CSS to enhance oil recovery will be more pronounced in oil layers with lean solution gas. In addition, normal air injection can be a viable choice considering the free availability of air, and injection of oxygen-reduced air can become a good option for ultra heavy oils featured with poor LTO reactivity for the sake of safe production.

Solvent-Based and Solvent-Assisted Recovery Processes: State of the Art

Summary Steam injection is a widely used oil-recovery method that has been commercially successful in many types of heavy-oil reservoirs, including the oil sands of Alberta, Canada. Steam is very effective in delivering heat that is the key to heavy-oil mobilization. In the distant past in California, and also recently in Alberta, solvents were/are being used as additives to steam for additional viscosity reduction. The current applications are in field projects involving steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS). The past and present projects using solvents alone or in combination with steam are reviewed and evaluated, including enhanced solvent SAGD (ES-SAGD) and liquid addition to steam for enhancing recovery (LASER). The use of solvent in other processes, such as effective solvent extraction incorporating electromagnetic heating (ESEIEH) and after cold-heavy-oil production with sand (CHOPS), are also reviewed. The theories behind the use of solvents with steam are outlined. These postulate additional heavy-oil/bitumen mobilization; oil mobilization ahead of the steam front; and oil mobilization by solvent dispersion caused by frontal instability. The plausibility of the different approaches and solvent availability and economics are also discussed.

Effect of physical heating on productivity of cyclic superheated steam stimulation wells

Previous works have focused on the single factor analysis of the effects of chemical reactions of superheated steam with oil and rock minerals on the oil well productivity. However, the relationship between the factors and the contributions to productivity is still unknown. In this paper, the contribution of physical heating of superheated steam to well productivity is studied with the numerical method. Results show that: (a) the heat in the area has a very limited increase when the temperature of superheated steam continues to increase. (b) At the starting stage, the oil is heated to a higher temperature and the mobility is increased. The elastic energy becomes the dominant factor controlling the productivity of the oil well in the following stage. (c) The chemical reactions of superheated steam with oil and rock minerals are the dominant factors contributing to the productivity.

New analytical equations for productivity estimation of the cyclic CO2-assisted steam stimulation process considering the non-Newtonian percolation characteristics

The research course in the estimation of productivity of cyclic steam stimulation wells can be divided into three stages: (a) the mobility of heavy oil in the cold area is neglected, (b) the mobility of heavy oil in the cold area is considered—however, it is Newtonian fluid seepage, and (c) it is conserved as non-Newtonian fluid seepage in the cold area. However, the distribution of the value of starting pressure gradient in the heated area where heavy oil is still non-Newtonian fluid is neglected. In this paper, a new model is developed for productivity estimation of cyclic steam stimulation wells with consideration of the non-Newtonian fluid flow behaviors in the heated area where the temperature is higher than the turning point. New percolation equations are developed based on the new proposed concept of “the transition region” in the heated area. The results show that: (1) when the non-Newtonian fluid characteristic is neglected, the predicted results from the new model match the results from the numerical simulator perfectly, and (2) in oil field, the non-Newtonian fluid characteristic cannot be neglected. When the non-Newtonian fluid characteristic is considered in the model, the average oil production in each cycle can match the filed data better than Yang et al.’s model. This new model laid a basic reference for oil companies and researchers involved in the area when they are designing the well pattern, spacing or estimating the productivity of oil wells.

A New Mathematical Model For Heat Radius of Cyclic Superheated Steam Stimulation with Horizontal Wellbore

When superheated steam flows along the horizontal wellbore, it may change to saturated steam at some point of the wellbore. In this paper, to accurately predict the heat radius of cyclic superheated steam stimulation with horizontal wellbore, the distribution of thermophysical properties of superheated steam along the horizontal wellbore is considered. The heating process is divided into 4 stages for superheated steam and 3 stages for saturated steam when the phase change undergoes in the wellbore. On this basis, the mathematical model for heat radius of cyclic superheated steam stimulation with horizontal wellbore was established according to energy conservation principle and Laplace transformation method. The calculation result of the new mathematical model is in good agreement with that of the numerical simulation (CMG STARS) for the same parameters from a specific heavy oil reservoir, which verified the correctness of the new mathematical model. The effect of degree of superheat and the cycle of stimulation are analyzed in detail after the new mathematical model is validated. The results show that the heat radius of superheated zone, steam zone, and hot fluid zone all decrease with horizontal well length and increase with the cycle of stimulation. The higher the degree of superheat is, the farther from the heel of the horizontal wellbore the phase change undergoes. Besides, the radius of superheated zone, steam zone, and hot fluid zone increases with the degree of superheat, but the value increases little at steam zone and hot fluid zone.

A novel model and sensitive analysis for productivity estimate of nitrogen assisted cyclic steam stimulation in a vertical well

Nitrogen-assisted cyclic steam stimulation (NCSS, i.e. huff and puff) is an important alternative to recover heavy oil reservoirs. In order to forecast the production performance accurately and rapidly, a novel model is developed for heated radius calculation and production prediction of NCSS wells. The underlying assumption in this paper is different from the Marx-Langenheim isothermal model, the heated area is assumed to be non-isothermal and the temperature decreases exponentially. A new heated radius calculation equation is then established and solved by the Newton iteration method. Afterwards, an analytical model for production prediction is derived with pseudo-steady state percolation method by considering the variation of temperature, pressure, relative permeability, etc. during the different periods of the huff-n-puff process. After verification by numerical simulation runs, a sensitivity analysis is performed with the consideration of multiple factors, such as injection rate, injection temperature, fluid component and threshold pressure gradient (TPG). The results indicate that the increase of injection rate, injection temperature and nitrogen-steam ratio, or the decrease of TPG will lead to an increase in oil production. This paper provided a reference for heated radius evaluation and productivity estimation in NCSS processes for heavy oil.

Monitoring of cyclic steam stimulation by inversion of surface tilt measurements

Temperature and pressure changes associated with the cyclic steam stimulation (CSS) used in heavy oil production from sands are accompanied by significant deformation. Inversion of induced reservoir pore-pressure changes from deformation measurements may provide a potentially powerful reservoir-monitoring tool if the issues of measurement noise, uncertainty in model parameterization, and numerical accuracy and stability can be resolved. We discuss inverting injection-induced reservoir pressure changes from observable surface deformations using a linear poroelastostatic model of a heavy oil reservoir. We also present results of inversion from surface tilt measurements taken at a production site undergoing CSS. We demonstrate that a stable inversion of the reservoir pore-pressure change can be achieved from sparse and noisy surface tilt measurements using constrained regularized optimization. The results provide an insight into the heterogeneity of reservoir stimulation and could help with optimizing well locations and stimulation protocols.

Supercritical cyclic steam stimulation of wellbore temperature and pressure distribution in Lukeqin oilfield

Supercritical cyclic steam stimulation of wellbore temperature and pressure distribution in Lukeqin oilfield

Energy efficiency and greenhouse gas emissions of current steam injection process and promising steam based techniques for heavy oil reservoirs

Steam injection process has been the prevailing technique for heavy oil and bitumen extraction in the past decades, but the recovery performance and energy efficiency are poor, especially in oil reservoirs with harsh conditions and severe heterogeneity. With global requirements on energy conservation and emission reduction, it is of great significance to improve current techniques or find new techniques to promote the energy efficiency of steam injection process and mitigate associated greenhouse gas emissions. In this study, the energy efficiency and CO2 emissions of current steam injection processes were evaluated, along with sensitivity analysis of various influencing factors. Cyclic steam stimulation (CSS) process was taken as an example to study the production and energy efficiency performance of steam injection. The results show that the steam to oil ratio, energy intensity and CO2 emissions all rise with the increasing crude oil viscosity, but fall with the increase of oil saturation, reservoir temperature, bottom hole steam quality and reservoir heat efficiency. Field history analysis about CSS process shows that the production performance of CSS process was dominated by different factors with the proceeding of oil production, and gas injection assisted CSS process can effectively enhance oil recovery, improve energy efficiency and mitigate CO2 emissions. Finally, the improved steam injection techniques are discussed to shed some lights on the efficient exploitation of heavy oil reservoirs.