Multilateral Wells Research Articles

Recommendations for the multilateral wells design selection in various geological conditions based on lessons learned

The authors of the article have summarized the experience of multilateral well application, performed an efficiency analysis of multilateral wells vs horizontal wells in Rosneft Oil Company's fields with various subsurface architecture. The algorithm for multilateral well efficiency estimation, compared to other type of well completions, was developed. This algorithm is based on the selection of areas for well locations with similar reservoir properties, reservoir energy conditions, and reservoir development conditions to evaluate production startup parameters, decline rates, cumulative parameters for the areas of over 6 month production. A matrix of multilateral well applicability in various geological conditions was generated, and recommendations for preferable well design were made. This type of analysis was conducted for the first time due to collection of sufficient statistical data, because of a multiple increase in the amount of drilling complex wells in the recent years. The obtained results provide an opportunity to design an efficient field development system for new assets, perform an adjustment of brownfields development systems, select multilateral well design for certain geological conditions based on lessons learned.

Intensification of development of Garbi Absheron field, drilling of multilateral wells and efficiency estimation

The paper presents detailed feasibility on improvement of traditional well drilling technology and development systems in accordance with the development plan of Garbi Absheron field. It is noted that the most optimum option of art-of-the-state technologies and approaches to the field development is the drilling of horizontal and multilateral wells with the purpose of efficient completion of recovered resources and intensification of field development. The drilling and putting on production of such wells are considered cost-effective as well. Thus, the optimum amount and type of wells in existing and new platforms for ensuring efficient field development are specified.

Combined stochastic and discrete simulation to optimise the economics of mixed single-horizontal and multilateral well offshore oil developments

Multilateral wells promise cost savings to oil and fields as they have the potential to reduce overall drilling distances and minimize the number of slots required for the surface facility managing the well. However, drilling a multilateral well does not always increase the flow rate when compared to two single-horizontal wells due to competition in production inside the mother-bore. Here, a holistic approach is proposed to find the optimum balance between single and multilateral wells in an offshore oil development. In so doing, the integrated approach finds the highest Net Present Value (NPV) configuration of the field considering drilling, subsurface, production and financial analysis. The model employs stochastic perturbation and Markov Chain Monte-Carlo methods to solve the global maximising-NPV problem. In addition, a combination of Mixed-Integer Linear Programming (MILP), an improved Dijkstra algorithm and a Levenberg-Marquardt optimiser is proposed to solve the rate allocation problem. With the outcome from this analysis, the model suggests the optimum development including number of multilateral and single horizontal wells that would result in the highest NPV. The results demonstrate the potential for modelling to find the optimal use of petroleum facilities and to assist with planning and decision making.

Application of drilling of multilateral well on the basis of new technology and model in south Caspian basin

The article discusses the issue of drilling multilateral horizontal wells and provides a brief history of its development. Data were provided on the selection of the location of the multilateral horizontal well, drilling the main wellbore and determining the depth for running the сasing strings. This paper also analyzes the selection of lateral wellbore penetration depth, the importance of drilling multilateral horizontal wells and their application for the first time in the shelf water of South Caspian Basin, at the Western Absheron field, Well 19. Keywords: multilateral wells; drilling of horizontal wells; petrophysical models; drilling of main and lateral wellbores.

Application of Multilateral Wells for Production and Enhanced Oil Recovery: Case Studies from Canada

Summary The use of multilateral wells started in the mid-1990s in particular in Canada, and they have since been used in many countries. However, few papers on multilateral wells focus on their production performance. Thus, what can be expected from such wells in terms of production is not clear, and this paper will attempt to address that gap. Taking advantage of public data, the production performance of multilateral wells in various Western Canadian fields has been studied. In the cases reviewed in this paper, these wells always target a single formation; they have been used in a variety of fields and reservoirs, mostly for primary production but also for polymer flooding in some cases. Multiple examples will be provided, mostly in heavy oil reservoirs, and production performance will be compared with nearby horizontal wells whenever possible. From the more classical dual and trilateral, to more complex architectures with seven or eight laterals, and the more exotic with laterals drilled from laterals, the paper will present the architecture and performance of these complex wells and of some fields that have been developed almost exclusively with multilateral wells. Interestingly, multilateral wells have not been used much for secondary or tertiary recovery, probably because of the difficulty of controlling water production after breakthrough. However, field results suggest that this may not be such a difficult proposition. One of the most remarkable wells producing a 1,250-cp oil under polymer flood has achieved a cumulative production of more than 3 million bbl, which puts it among the top producers in Canada. Although multilateral wells have been in use for more than 25 years, very few papers have been devoted to the description of their production performance. This paper will bring some clarity to these aspects. It will also attempt to address when multilateral wells can be used and to compare their performance to that of horizontal wells in the same fields. It is hoped that this paper will encourage operators to reconsider the use of multilateral wells in their fields.

Numerical Simulation of Natural Gas Hydrate Exploitation in Complex Structure Wells: Productivity Improvement Analysis

About 90% of the world’s natural gas hydrates (NGH) exist in deep-sea formations, a new energy source with great potential for exploitation. There is distance from the threshold of commercial exploitation based on the single well currently used. The complex structure well is an efficient and advanced drilling technology. The improvement of NGH productivity through various complex structure wells is unclear, and there is no more complete combing. Thus, in order to evaluate their gas production characteristics, we establish a mathematical model for exploitation of NGH, and then 13 sets of numerical models based on the geological parameters of the Nankai Trough in Japan are developed and designed, including a single vertical well, a single horizontal well, 1~4 branch vertical wells, 1~4 branch horizontal wells, and 2~4 branch cluster horizontal wells. The research results indicate that wells with complex structures represented by directional wells and multilateral wells can significantly increase the area of water and gas discharge, especially cluster wells, whose productivity can be increased by up to 2.2 times compared with single wells. Complex structural wells will play an irreplaceable role in the future industrialization of NGH.

The Adverse Impact of Muddy Laminae on Conventional SAGD Performance and Improvement Strategy with the Multilateral Well Pattern

With further progress of Steam-Assisted Gravity Drainage (SAGD) technology, a growing number of oil sands or heavy oil reservoirs were put into production in an efficient way. However, owing to the existence of muddy laminae within reservoirs, there are challenges associated with the expansion of the steam chamber and oil drainage during the SAGD process. The purpose of this study is to evaluate the adverse impact of muddy laminae on conventional SAGD performance and introduce an improvement strategy with multilateral well patterns to reduce the adverse impact and improve the performance. In the research reported here, the reservoir numerical simulation approach is applied to conduct the research. The analysis conducted on a prototypical reservoir reveals that the steam chamber may expand slowly in some sections due to the poor capacity of heat and mass transfer, and the expansion of the steam chamber is relatively uneven along the wellbore, when the muddy laminae are existing in the formation. The influence level of the muddy laminae on conventional SAGD performance under different distribution modes is different, but the adverse effect is mainly reflected in the delay of peak oil production, the decrease in peak oil production, the decrease in steam chamber volume, and the increase in the cumulative steam oil ratio (mainly in early and middle stages of the SAGD process). On the basis of aforementioned researches, the improvement strategy with two different multilateral well patterns, planar multilateral well and upward multilateral well, is introduced to improve the SAGD performance. The results indicate that the combination of a planar multilateral injector and planar multilateral producer has the best performance. By adopting such kind of combination, the recovery factor can be increased from 31.36% to 47.08%, and the cumulative steam oil ratio can be decreased from 5.29 m3/m3 to 4.64 m3/m3 under the combined distribution mode of muddy laminae. It can be known that the branches of the planar multilateral well are very helpful for the expansion of the steam chamber and oil drainage, once the heat connection between branches of the injector and producer is well established. Overall results show that the multilateral well pattern is promising for SAGD applications at oil sands or heavy oil reservoirs which are rich in muddy laminae.

Numerical Investigation on Gas Production Performance in Methane Hydrate of Multilateral Well under Depressurization in Krishna-Godavari Basin

Nature gas hydrate is a new kind of clean and potential resources. Depressurization is regarded as the most effective and promising hydrate production technology. One of the key points in improving the gas production effectiveness of depressurization is whether pressure gradient could transmit in strata effectively. Single well method is widely used in hydrate exploit which is circumscribed in expanding the range of hydrate decomposition. Consequently, the well structure and production strategy needs to be optimized for improving the gas recovery efficiency. The multilateral well technology is proposed for increasing the gas productivity of the reservoir greatly by increasing the multilateral branches. In this paper, we established a numerical simulation model based on the geological data NGHP-02-16 site in the KG basin to evaluate the gas production performance of the reservoir by depressurization. It mainly focuses on investigating the gas production performance of multilateral wells with different combinations of geometric parameters of multilateral branches, such as different dip angle, numbers, and spacing of lateral branches. The result shows that the multilateral well method can effectively increase the gas production rate with the water production rate increase slightly. The cumulative gas production volume of a single vertical well is about 2.85 × 10 6 m 3 , while it is of the multilateral well can reach 4.18 × 10 6 m 3 during a one-year production. The well interference, the effective influence radius of each multilateral branch, and the vertical depth of the lateral branch are the main factors which affect the gas production efficiency of the multilateral well. The optimization of the geometric parameters of lateral should consider not only the gas production efficiency but also the well interference between the lateral branches.

Completion, development and prospects of multilateral wells

The paper reviews the completion and development of multilateral horizontal wells. Brief data on location schemes of multilateral horizontal wells and completion levels is presented as well. At the same time, the paper analyzes the significance of drilling multilateral horizontal wells in the modern experience of oil and gas production, and their first implementation on the shore of South Caspian in the well No 19 of Garbi Absheron field.

Numerical study of gas production from fine-grained hydrate reservoirs using a multilateral horizontal well system

Natural gas hydrate is prevalent in ultralow-permeability fine-grained sediments with substantial reserves. However, effective and safe gas production from fine-grained hydrate reservoirs remains a global challenge. Here, a multilateral horizontal well system is innovatively employed to improve production efficiency in fine-grained hydrate reservoirs. A three-dimensional (3D) numerical model of a real gas hydrate reservoir is constructed, and the influences of well configuration, deployment location, depressurization pressure, and reservoir properties on production are systemically and quantitatively evaluated. The spatial distributions of the physical properties of the 3D reservoirs during gas production are clearly revealed. The results indicate that the production efficiency of multilateral horizontal wells improves with increasing branch number and length, particularly when the ratio of branch length to reservoir width exceeds 0.15. Branch interference and perforation length positively affect production enhancement when multilateral horizontal wells are deployed in hydrate reservoirs with specific ultralow permeabilities; these discoveries are revealed for the first time. Multilateral horizontal wells with helically and vertically distributed equal-length branches yield high production efficiencies, and their optimal locations are in the lower sections of the reservoirs, particularly within high-isotropic-permeability reservoirs. Moreover, uniformly low depressurization pressure in helically distributed branches facilitates gas extraction; gas recovery efficiency increases by 8% when production pressure decreases by 1 MPa. This study suggests that the use of a helical multilateral well system is a promising strategy for achieving commercial gas production from fine-grained hydrate reservoirs.

Design and productivity evaluation of multi-lateral well enhanced geothermal development system

Enhanced geothermal development system is an effective means to develop hot dry rock geothermal resources, and its reasonable structural design is crucial to the efficient exploitation of hot dry rocks. In this paper, a multi-lateral well enhanced geothermal development system, which is composed of one low-permeability thermal reservoir, three multi-lateral injection wells, three multi-lateral production wells and three artificial fractures, was designed based on the traditional dual-well development model. Then, a 3D hydrothermal coupling numerical evaluation model was established by using the local heat balance method, and its accuracy and reliability were verified according to Lauwerier analytical theory of fractured flow and heat transfer. Finally, the influence of reservoir parameters, well layout parameters, and injection-production parameters on the heat production performance of this enhanced geothermal development system were explored based on the water-rock coupling mechanism inside the reservoir in the process of thermal production. And the following research results were obtained. First, the “rock invasion effect” of the cold front in the fractures of the multi-lateral well development system is stronger than that in the matrix. Increasing the reservoir permeability can improve the internal heat transfer effect, but also enhances the “invasion performance” of cold front. Second, the annual thermal energy extraction of the system gradually decreases over time and it also decreases with the increase of the injection temperature. It increases with the increase of the reservoir permeability in the early stage of the operation, but decreases greatly after the completion of the thermal breakthrough. Third, the system's thermal energy extraction rate and production mass flow rate are less influenced by reservoir porosity and injection temperature, but they decrease with the increase of the vertical spacing of injection-production wells. Fourth, the production temperature decreases greatly with the increase of the reservoir permeability, increases with the increase of the reservoir porosity, and decreases with the decrease of the vertical spacing of injection-production wells. Fifth, the heat production performance of the system in the early stage can be improved by increasing the length of the production well, and the heat production capacity of the system can be enhanced to a certain degree by increasing the injection-production pressure difference, but excessive pressure difference will impact the service life of the reservoir seriously.

Determination of well spacing volumetric factor for assessment of final oil recovery in reservoirs developed by horizontal wells

The formula for determination of volumetric factor of well spacing for assessment of final oil recovery in reservoirs developed by horizontal wells is offered. For the purpose of comparison of well spacing calculated using conventional and volumetric techniques, twelve development options of the pilot area of the Yamashinskoye field with variousplacement of vertical and horizontal wells were considered. By results of calculations, marked difference in values of well spacing was observed testifying that the conventional formula used to calculate well spacing does not consider the volume nature of fluid inflow to wells with one or more horizontal laterals. The offered technique of volumetric determination of well spacing through the inclination angle, the radius of well drainage area, and the length of a lateral considers the volumetric nature of inflow to horizontal multilateral wells.

Study on heat extraction considering the number and orientation of multilateral wells in a complex fractured geothermal reservoir

Understanding the flow and heat transfer in fractured geothermal reservoir is critical for the development of enhanced geothermal system (EGS) in the future. Under the framework of discrete fracture network, a thermal-hydraulic coupled model is proposed to evaluate the heat extraction performance of multilateral wells in fractured reservoirs. Five cases with varying numbers of branch wells considering well orientation are compared. In addition, we analyze the heat extraction performance response of multilateral wells in fractured reservoirs to the operating parameters. Results demonstrate the minimal effect of the increasing number of branch wells on the production temperature, while impacts on the well pressure are much greater. The injection pressure is observed to decrease significantly as the number of branch wells increases, resulting in a reduced reservoir flow resistance and increased net thermal energy by reducing pump energy consumption. For the same case, increasing the number of intersections between wells and fractures reduces the production temperature and injection pressure. Parameter sensitivity analysis reveals heat production to increases with the mass flow rate, well length and well spacing, and decreases with increasing fracture permeability. This study is expected to provide a view for the application of multilateral wells in fractured geothermal reservoirs.

Horizontal Wells: Applications, Considerations, and Case Histories

This paper discusses many aspects of the application of horizontal wells for field development, starting with the basic question of why to opt to this technology. The different considerations to be taken into account when dealing with the technology are reviewed, including some inherent downsides like higher cost and operational complications. The main emphasis, however, is placed on practical reservoir engineering aspects, including well planning and performance, and the handling of horizontal wells in specific technical applications like well test
 analysis and numerical modeling.
 
 
 
 The theoretical basis and pertinent differences in physics and flow regimes around vertical and
 horizontal wells are discussed in the context, together with the inherent practical implications.
 Case histories and examples are presented for several successful applications worldwide that the author was involved in. In one case, a medium size field offshore Canada was developed with waterflood utilizing very few horizontal producers, with a set of horizontal and vertical water injectors. Detailed planning and intensive modeling, carried out by a team of engineers and geoscientists, led to a remarkably
 successful field development. In another case, few horizontals were used among many directional wells to develop a Mediterranean oil reservoir under aquifer and gas cap drives in an attempt to reduce coning problems, raising an opportunity to compare the long term performance of different geometry wells.
 A brief description is also presented to some advanced techniques and special cases of implementing horizontal wells such as thermal recovery (Steam-Assisted-Gravity-Drainage, or SAGD Process), multi-lateral wells, and multi-fractured wells, with discussion on these applications. Under favorable conditions, horizontal wells can also be used as an Improved Oil Recovery (IOR) tool in mature fields, an application that became very common in many super giant fields in the Arabian Gulf Area.

Prospect of marine natural gas hydrate stimulation theory and technology system

The key to realize the commercial production of natural gas hydrate (NGH) is to increase theNGH productivity significantly in the scale of magnitude. Whether NGH production can be commercialized depends on two aspects. The first is whether the in-situ recoverable reserves are large enough to support the basic production period for commercial production. The second is whether the average productivity can reach the standard for commercial production. In this paper, we will analyze mainly about the potential stimulation technologies for NGH development, and discuss about the basic principles, the evaluation methods, and the technical bottlenecks for NGH production and stimulation. The results indicate that the main mechanisms for increasing theNGH productivity are in three respects, namely enlarging the drainage area, increasing the NGH dissociation efficiency, and improving the seepage conditions. With complex-structure wells and multiple-well patterns, combined with novel production methods and/or reservoir stimulation technologies, the NGH productivity can be increased greatly. Particularly, the complex-structure wells and well patterns are very important for increasing NGH productivity. With complex-structure wells and well patterns, combined with heat injection and/or reservoir stimulation, NGH productivity can be increased on a magnitude scale. Currently, in fundamental researches, there are some technical bottlenecks for the studies of NGH production, mainly in sample preparation, simulated reservoir monitoring, and mechanical coupling technologies. Therefore, it is suggested that the study focuses should be on the above technical bottlenecks during the basic research on how to increase the NGH productivity. It is concluded that the combined application of complex-structure wells (horizontal wells and multi-lateral wells), well-pattern production models (with multi-cluster/group well production), the novel production methods (mainly thermal stimulation, together with depressurization), and reservoir stimulation technologies (hydraulic fracturing) are the keys to increase NGH productivity in the scale of magnitude.

Reservoir and Wellbore Flow Coupling Model for Fishbone Multilateral Wells in Bottom Water Drive Reservoirs

AbstractNowadays, different types of complex production wells are applied in challenging reservoirs in order to maximize oil recovery. A representative application is the fishbone multilateral horizontal wells, which have advantages of expanding the drainage area information and reducing the pressure loss in the long single lateral wellbore. This paper investigated the performance of fishbone wells and derived a wellbore and reservoir flow coupling model for fishbone multilateral wells in the bottom water reservoirs. The new model considered plenty of parameters that may have significant impacts on productivity and pressure drop in the well, including the fishbone structure, the main and branch wellbores’ length, the spacing distance of the branch wellbores, wellbore radius, and preformation parameters. Furthermore, a sensitivity analysis example by the numerical method is presented in this paper. Compared with other models, our coupling model, when it is degraded to horizontal well, is more consistent with the results of actual field situation. In another comparative analysis, the results of the new model with branches show a good match with the numerical simulation results by software. The proposed method in this paper can be used as a valuable tool to analyze the productivity, wellbore inflow profile, and pressure profile of the fishbone multilateral wells in the bottom water reservoir.

Numerical simulation investigations of coalbed methane drainage performance with multilateral well

A novel multilateral well for coalbed methane extraction was proposed in the study. There is a main wellbore at the longitudinal center of coal seam and four lateral wells at the horizontal center in the multilateral-well system. Compared with traditional drainage holes, multilateral-well system has a better performance on coalbed methane development. A hydraulic-mechanical coupling model of multilateral well was established, the pressure and permeability ratio distribution of the gas extraction process were analyzed comprehensively. The sensitivity analysis of lateral number, length distribution and intersection angle of multilateral-well system were studied. The results indicate that there is a minimum gas pressure distribution around the multilateral well and the overall permeability of coal seams increases with production time and the permeability around the multilateral well is larger than the area away from the multilateral well which induced by the gas desorb and matrix shrink. The quantity of lateral wells has a positive effect on cumulative production. When the total length of lateral wells is equal, the uniformity and symmetry of lateral length distribution are two key factors on the gas extraction performance. The minimum intersection angle has a positive effect on cumulative production. This study provides a better alternative for traditional drainage hole to obtain greater coalbed methane performance.

High-Density Brine Used in Oil-Based Completion Fluid Deployed Offshore Norway

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 199243, “First Use of a Newly Developed High-Density Brine in an Oil-Based Screen Running Fluid in a Multilateral Extended-Reach Well: Fluid Qualification, Formation Damage Testing, and Field Application, Offshore Norway,” by Bjarne Salmelid, Morten Strand, and Duncan Clinch, Halliburton, et al., prepared for the 2020 SPE International Conference and Exhibition on Formation Damage Control, Lafayette, Louisiana, 19–21 February. The paper has not been peer reviewed. When used for running sand-control screens, low-solids, oil-based completion fluids (LSOBCF) maintain reservoir wellbore stability and integrity while minimizing the potential risks of losses, screen plugging, completion damage, and productivity impairment. Until now, using LSOBCF as a screen running fluid has been limited by fluid density. The complete paper discusses the design, qualification, and first deployment of an LSOBCF that incorporates a newly developed, high-density brine as the internal phase to extend the density limit. Field History This new field’s well forms part of the greater Alvheim area located in the central part of the North Sea, close to the UK sector. The formations discussed present excellent reservoir characteristics but also significant drilling challenges. The intruded country rock tends to have a high shear failure gradient (SFG) combined with a relatively low fracture gradient. Furthermore, because these reservoirs are exploited using long horizontal and multilateral wells, the drilling window is relatively narrow. For the presented case, the SFG was anticipated to be 1.39 specific gravity (SG) equivalent mud weight with an equivalent circulating density limit of 1.49 SG and stretch limit of 1.53 SG. The fluid density chosen to drill the well was 1.40 SG, and the density for the screen running fluid was planned to be 1.45 SG. Fluids Qualification Laboratory Testing Matrix. An extensive laboratory test matrix was initiated for the qualification of reservoir fluids. The reservoir fluid and drill-in fluid (RDIF) qualification is not detailed in the paper, only the LSOBCF and the novel brine used to prepare this fluid. The test matrix included tests such as rheology performance, long-term stability, production screen on 275 µm screen coupons, standard fluid-loss and filter-cake repair capabilities, reservoir fluid and RDIF compatibility tests, true crystallization temperature (TCT), and corrosion rate. The ultimate test was to check for formation and completion damage performance.

Effect of Well Orientation on Oil Recovery from Waterflooding in Shallow Green Reservoirs: A Case Study from Central Africa

Recovery efficiency is a key factor in decision-making in oil and gas projects. Although structural setup and well type considerably influence waterflood recovery, few studies have explored the performance of highly deviated wells during the waterflooding of complex shallow reservoirs. Here, we applied numerical simulations to investigate the performance of vertical, horizontal, multilateral, and highly deviated wells during waterflooding of complex shallow reservoirs using the J1 Oilfield as a case study. Recovery efficiencies of 31%, 33%, 31%, and 26% could be achieved for vertical, horizontal, multilateral, and highly deviated wells, respectively. The gas production rate was 39% higher in the vertical wells than in the other types. Highly deviated wells yielded the highest water-cut (80%) over a short period. Highly deviated wells delivered the least production, and, despite branching laterals, multilateral wells were also not the most productive. Our results provide insights into the performance of different well types during the waterflooding of green heterogeneous non-communicating reservoirs and present an example of the successful practical application of waterflooding as an initial recovery mechanism when oil is near the bubble point. This study indicated that multilateral wells are not a panacea in reservoir development. Highly deviated wells are the ideal choice for the shallow, heterogeneous non-communicating reservoirs when economic and environmental impact are considered in decision-making. Well design should be a case-by-case study considering reservoir characteristics, economics, and environment impact.

Особенности промыслово-геофизических и гидродинамических исследований горизонтальных многозабойных скважин на месторождениях ПАО «НК «Роснефть»

Особенности промыслово-геофизических и гидродинамических исследований горизонтальных многозабойных скважин на месторождениях ПАО «НК «Роснефть»