Multibranch Wells Research Articles

Numerical modeling and the ultimate bending experiment of the directional drill pipes bending at the dog-leg of the multi-branch well

Directional drill pipes are prone to failure in the fish-bone branch wells. The primary cause of the directional drill pipes failure is excessive bending. This paper established a mathematical analysis model for the bending stress of the directional drill pipes at any point along its trajectory. Tested the mechanical properties of the directional drill pipe. An ultimate bending experiment was conducted on the directional drill pipes based on the pure bending moment theory. Additionally, a non-linear finite element model(FEM) of the directional drill pipes was established to analyze the influence of different bending loads on the stress distribution of the directional drill pipes connection. The FEM results were consistent with the results of the ultimate bending experiment. The FEM results indicate that the Box bending under transverse force is the primary cause of the failure for the Tooth top. The research results enable engineers and operators to easily obtain the stress distribution of the directional drill pipes under borehole curvature.

Increasing the efficiency of the development of hard-to-recovery oil and gas condensate field reserves by constructing multilateral horizontal wells

At present, a significant number of Russian fields have hard-to-recover hydrocarbon reserves. The share of hard-to-recover reserves in our country accounts for more than 65% (or 12 billion tons) of oil and gas reserves on the balance sheet (in categories A + B + C1). To develop hard-to-recover re-serves successfully, it is necessary to nurture technical and technological potential because the cur-rent technological base of the Russian Federation does not meet the growing demand. The industry requires the development of new approaches concerning exploration, drilling and enhanced oil re-covery. New technologies will make it possible to start developing unique deposits in new regions. That is why the task of implementing new effective technological solutions, which will allow hard-to-recover and low-margin hydrocarbon reserves development, is relevant today. One of the ad-vanced technological solutions is drilling multilateral horizontal wells. That can significantly increase the flow rates. Keywords: hard-to-recover reserves; development stimulation; development of low-permeability reservoirs; multilateral wells; multibranch wells; optimal length of the horizontal rathole; Fishbone well.

Exploitation technology and productivity analysis of hydrothermal geothermal multi-branch wells

At present, hydrothermal geothermal mining mainly adopts wells recharge mode, and the structure of production and irrigation wells are mainly vertical wells, which rarely used in related horizontal wells. Moreover, domestic hydrothermal geothermal injection and production technology have low productivity and low utilization potential, so it is urgent to carry out corresponding research and tackle key problems of new technologies such as branch wells to improve the development potential and utilization value of geothermy. In this work, the mining scheme and productivity of heat storage branch wells in Guanzhong Basin are analyzed and studied by numerical simulation. Aiming at the distribution of geothermal resources in Guanzhong Basin, a geothermal branch wells scheme was proposed, and the influence of horizontal wells branch number, branch direction and location, branch wells structure and other factors on the productivity of the whole mining system were studied. The results show that the heat recovery power of multi-branch wells not only increases by 60 % compared with that of vertical wells structure in the case of this work, but also improves recharge and recovery effectively. The heat recovery power of the fishbone lateral horizontal wells was increased by about 30 % during its life cycle. The effects of multi-lateral wells structure parameters on productivity and thermal diffusion were systematically analyzed to further clarify the optimization direction of heat reservoir lateral wells structure.

Enhanced gas production from silty clay hydrate reservoirs using multi-branch wells combined with multi-stage fracturing: Influence of fracture parameters

Natural gas hydrates are typically deposited in low-permeability clayey-silty sediments with low gas production. The two main methods for enhancing gas production are complex structural wells and hydraulic fracturing. However, using only one of those methods does not significantly increase gas production. Herein, a method of combined multi-branch well with multi-stage fracturing was proposed. A novel evaluation method for increased gas production under fracturing was first proposed to reveal the effects of fracturing domain area and number. Then five fracturing distribution models were designed and analyzed. Results indicate that the combined method increased the gas recovery ratio by 829.13% and the hydrate dissociation ratio by 710.34% compared to branching wells because of enlarging pressure propagation and communicating deep thermal fluids. The dissociation of hydrates is enhanced by an increase in the area and the number of fractures, but the rangeability of the increased stimulating effect declines. Different fracture distributions influence production performances at different stages. Short-term production is beneficial when fractures are in the branch well centers. Long-term gas production can be improved when fractures are mainly located at the branch distal end. This novel study has important implications for commercial exploitation at different production stages.

Enhanced gas production from low-permeability hydrate reservoirs based on embedded discrete fracture models: Influence of branch parameters

The low permeability of marine hydrate reservoirs makes it difficult for trail results to meet the demand for exploitation. Hydraulic fracturing and multi-branch wells are the primary methods for enhancing productivity. This study proposed a new production enhancement method of multi-branch wells combined with multi-stage fracturing (MWMF) based on the embedded discrete fracture model (EDFM). By simulation of the Shenhu area, the multi-physical field evolution of the MWMF production process was first revealed, followed by the systematic analysis of the MWMF production enhancement effect with branch parameters. Results indicated that the cumulative gas production of MWMF increased by 327% compared with only horizontal wells. The production of four-branch wells exhibited a 7% reduction compared to horizontal wells using the MWMF method, suggesting increased branch numbers inhibit production. Increasing branch length was positively correlated with enhanced production. Notably, the influence of branch length on gas production became more pronounced as the number of branches increased. The interface of the three-phase layer (TPL) and hydrate-bearing layer (HBL) was the most suitable location for branch well placement. This novel study provides valuable insights into new applications of the MWMF method in developing low-permeability hydrate reservoirs.

Two-phase geothermal model with fracture network and multi-branch wells

Two-phase geothermal model with fracture network and multi-branch wells

Study of Multibranch Wells for Productivity Increase in Hydrate Reservoirs Based on a 3D Heterogeneous Geological Model: A Case in the Shenhu Area, South China Sea

Summary So far, a total of 11 hydrate trial production projects have been carried out all over the world, all of which used a single vertical well or horizontal well to carry out hydrate production by the depressurization method or depressurization combined with other methods. These traditional production methods have some limitations: The single vertical well has a small contact area with the reservoir, and the transmission range of the temperature and pressure is limited; therefore, the productivity is low. The horizontal well can improve hydrate productivity from magnitude order; however, there is a long distance from the standard of commercial production of marine hydrate. Therefore, it is an inevitable trend to find a highly efficient and advanced drilling technology for heterogeneous hydrate reservoirs. The multibranch wells based on horizontal wells can not only increase the contact area between the hydrate reservoir and well by branch structure to improve the conductivity of the reservoir temperature and pressure but also improve the hydrate productivity by laying the branch at high hydrate saturation for areas with extremely uneven distribution. Therefore, for this paper, we chose the Shenhu area as the research area to establish an approximate realistic 3D heterogeneous geological model contained with hydrate, then we laid the multibranch wells based on horizontal wells in high hydrate saturation area and optimized the branch direction, location, and spacing, and the production increasing effect was assessed. Finally, an optimal multibranch well scheme was obtained under the conditions of this paper setting, which is as follows: The vertical multibranch well was set at the root end of the horizontal main well with a branch spacing of 10 m, and the productivity after optimization was 31.64% higher than that before optimization.

Bending Deformation and Ultimate Moment Calculation of Screen Pipes in Offshore Sand Control Completion

Horizontal wells, extended-reach wells, and multi-branch wells were often used to exploit subsea oil and gas efficiently. However, during the sand control screen completion of those wells, the sand control screen pipe was easily deformed. Failure occurred when passing through the bending section due to the large bending section in the wellbore trajectory. A parametric analysis model of the screen pipe was established based on ABAQUS and Python software under pure bending load first. Then, deformation patterns and mechanisms were identified and discussed. The effects of parameters on the screen pipe bending deformation patterns and the ultimate moment were analyzed. Finally, an empirical formula for calculating the ultimate moment of the screen pipe was established. The results showed that the deformation of the screen pipe was complex, and three deformation patterns were related to the hole parameters. Due to an increase in the diameter and number of circumferential and axial holes, the ultimate moment of the screen pipe gradually decreased, and the circumferential holes had a more significant effect on the ultimate moment than the axial holes. The established empirical formula could accurately calculate the ultimate moment of the screen pipe, and the average difference between the formula and numerical simulation results was 3.25%.

A new semi-analytical flow model for multi-branch well testing in natural gas hydrates

This paper presents a new semi-analytical solution and the related methodology to analyze the pressure behavior of multi-branch wells produced from natural gas hydrates. For constant bottom-hole pressure production, the transient flow solution is obtained by Laplace transforms. The interference among various branches is investigated using the superposition principle. A simplified form of the proposed model is validated using published analytical solutions. The complete flow profile can be divided into nine distinct regimes: wellbore storage and skin, vertical radial flow, linear flow, pseudo-radial flow, composite flow, dissociated flow, transitional flow, improvement flow and stress-sensitive flow. A well’s multi-branch structure governs the vertical radial and the linear flow regimes. In our model, a dynamic interface divides the natural gas hydrates deposit into dissociated and non-dissociated regions. Natural gas hydrates formation properties govern the compositeeffect, dissociated, transitional, and improvement flow regimes. A dissociation coefficient governs the difference in flow resistance between dissociated and non-dissociated natural gas hydrates regions. The dissociated-zone radius affects the timing of these flow regimes. Conversion of natural gas hydrates to natural gas becomes instantaneous as the dissociation coefficient increases. The pressure derivative exhibits the same features as a homogeneous formation. The natural gas hydrates parameter values in the Shenhu area of the South China Sea cause the prominent dissociated flow regime to conceal the later transitional and improvement flow regimes. Due to the maximum practical well-test duration limitation, the first five flow regimes (through composite flow) are more likely to appear in practice than later flow regimes. Cited as: Chu, H., Zhang, J., Zhang, L., Ma, T, Gao Y., Lee, W. J. A new semi-analytical flow model for multi-branch well testing in natural gas hydrates. Advances in Geo-Energy Research, 2023, 7(3): 176-188. https://doi.org/10.46690/ager.2023.03.04

Dynamic Distribution Characteristics of Oil and Water during Water Flooding in a Fishbone Well with Different Branch Angles.

Lab experiments, field pilots, and numerical modeling focusing on fluid flow aspects have indicated that multi-branch wells are technically effective and promising. Several researchers have conducted some experiments for a fishbone well strategy with mixed results. Our objective in this work is to study the impact of the different fishbone well patterns, such as branch angle, on the distribution of remaining oil after water flooding. In this paper, the interference effect between branches on oil recovery is studied in three steps. First, the interferences between fishbone wells with different branch angles were measured by hydro-electric simulation experiments. Second, two-dimensional visualization water flooding experiments were carried out to clarify the remaining oil distribution at different branch angles. Third, the distribution of oil and water in fishbone wells was verified by establishing a numerical model. The modeling results agree well with the experimental phenomena. At the same time, the variation trend of water and oil production in each branch is analyzed by numerical simulation results. The results indicate that the production is strongly dependent on the branch angles, and the highest recovery was 60.2% at a 45° branch angle.

Enhancement of gas production from low-permeability hydrate by radially branched horizontal well: Shenhu Area, South China Sea

A high gas production rate is critical for commercial exploitation of hydrate. Most marine hydrates deposit in the silty or clay sediments with low permeability, and gas production rate is low. Herein, a novel deployment of well, radial three-branch horizontal well was numerically investigated to enhance the gas production. A 3D geological model was established based on field trial in the Shenhu Area of the South China Sea. The simulation showed similar gas and water production for single and multi-branch horizontal wells with same length of 250 m. The depth in which well deployed dramatically affects the gas and water production, and which increases with the length of multi-branch well. Meanwhile the ratio of free gas originally distributed in three-phase and gas layers also increases with the length, which is 50% for 1200 m well. The interference around the intersection of branches enhances temperature recovery and the dissociation of underlying hydrates. The standard energy return on investment analysis shows that the economic potential increases linearly with the length of multi-branch well and obviously depends on the content of initial free gas. However, the production balances investment confines only to tens or hundreds of days for all model scenarios.

Production Behavior Analysis of Multibranched Horizontal Oil Well considering Reservoir and Well-Type Factors

Multibranched horizontal well is an important means to develop low permeability reservoirs. Fishbone multibranched horizontal well has the advantages of increasing drainage area, reducing drilling number, utilizing existing wells, and saving oilfield development cost, especially for marginal oilfield exploitation. The morphological structure of fishbone multibranched horizontal well is very complex, so the numerical simulation study is of great significance to guide the production of fishbone multibranched horizontal well. In this paper, the numerical model is established for fishbone multibranched horizontal well in the oil reservoir. The finite element method is used to numerically solve the mathematic model. The oil well production can be achieved by using the material balance method. Sensitivity analysis is made on the important reservoir and well-type factors that affect the production behavior and transient pressure distribution of fishbone multibranched horizontal well. It is concluded that the effective reservoir thickness and flowing bottomhole pressure have great influence on the productivity, but the influence of heterogeneity is not obvious. The length of main wellbore has great effect on the productivity in the early stage. Fishbone multibranched horizontal wells should be placed in the middle of the reservoir to increase productivity. Branch length, branch angle, branch number, and branch spacing are important parameters affecting the productivity of fishbone multibranched horizontal well. The variation of these parameters has obvious influence on the stimulation effect in the early stage of production, but the influence degree is different. Under the premise of drilling technology and drilling safety, the comprehensive impact of these four factors on productivity should be considered simultaneously. The presented model and obtained results not only enrich production behavior analysis of fishbone multibranched horizontal well but also have significance on formulation of stimulation measures and efficient low permeability reservoir development.

Numerical simulation of gas production from natural gas hydrate deposits with multi-branch wells: Influence of reservoir properties

Vast amounts of natural gas hydrate are buried in subseafloor sediments without impermeable boundaries, which is recognized as an essential energy source for the future. Previously, the multi-branch well was proposed to enhance the recovery efficiency of natural gas hydrate, and the gas production rate has been dramatically improved comparing with the vertical well. However, the multi-branch well shows a terrible performance in gas production duration. As a continuation of the previous study, numerical simulations were conducted to investigate the influence of hydrate reservoir properties on the gas production potential. Results indicate that it is hard to extract hydrate commercially for hydrate accumulations without impermeable boundaries. A high initial hydrate saturation leads to a long gas production duration but a low gas production rate. An increase in the intrinsic permeability of isotropic reservoirs would shorten the gas production duration and result in a low gas recovery ratio. Permeability anisotropy shows a noticeable effect on enhancing the gas recovery ratio and the gas production duration due to the improved pressure propagation pattern. Therefore, in the upcoming field tests, reservoir reconstructions that enhance permeability anisotropy are strongly suggested to obtain better outcomes.

Numerical simulation of gas recovery from natural gas hydrate using multi-branch wells: A three-dimensional model

Natural gas hydrate, a potential energy source, is clean and occurs abundantly in nature. Enhancing the gas production efficiency from gas hydrate-bearing sediments (GHBS) is of great significance to promote its industrial development. In this study, the radial jet drilling (RJD) technology is innovatively proposed to stimulate oceanic hydrate reservoirs. With an open-source simulator HydrateResSim, a 3D model is constructed based on the geological data from the SH7 site in the South China Sea. The hydrates exploitation performance using the combination of radial wells and depressurization is studied for the first time. Results indicate that radial wells can significantly enhance the gas production rate in the early stages of production. The hydrate recovery factor and the radial branch length are linearly related. However, the application of radial wells seems incapable of prolonging the gas production life cycle. By analyzing the multi-physical response of GHBS induced by depressurization, the stimulation mechanisms of radial wells are characterized as enlarged drainage area, enhanced pressure drop propagation, and increased geothermal heat flow. This work verified the capability of RJD in promoting hydrate extraction. Also, it provides insights into the potential applications of multi-branch wells in field trials of hydrate production.

Theoretical Approach for the Calculation of the Pressure Drop in a Multibranch Horizontal Well with Variable Mass Transfer.

In this study, the pressure drop obtained from physical experiments and theoretical approaches of a single horizontal wellbore is reviewed and a comprehensive wellbore pressure-drop model is derived for a multibranch well. We propose a new coupling model for fluid flow in multibranch wells and reservoirs. Based on this coupling model, we introduce a theoretical approach for the calculation of the pressure drop in a multibranch horizontal well with variable mass transfer. To facilitate the understanding of the physical model, the entire coupling model was divided into three parts: (1) the pressure-drop model of the wellbore, (2) the reservoir inflow model, and (3) the coupling model. By incorporating the acceleration, friction, mixing, confluence, and gravity pressure drops, a coupling model with a finite-conductivity multibranch horizontal well was developed. Newton–Raphson iterations and Visual Basic programming were employed to solve the coupling model and to obtain the pressure and the inflow rate of the wellbore. The wellbore pressure-drop model was verified by comparing it with different models for the same case study, which has been previously introduced in a different research work. Furthermore, the forecast and sensitivity analysis were conducted, and then the results are discussed. In the proposed new model, several factors are considered, including the wellbore structure, the wellbore completion method, the wellbore, and the fluids and formation properties. The presented approach can be used as a valuable tool to analyze the influence of the pressure drop on the productivity of complex-structured wells and vice versa, and to quantitatively investigate the various pressure drops in wellbores, including the friction, acceleration, mixing, confluence, and gravity pressure losses.

Experimental research on leaf vein geometric characteristics of multibranch horizontal well for coalbed methane recovery

AbstractThe similarity in the structure and function between leaf veins and multibranch wells provided the inspiration for a novel design of multibranch coalbed methane (CBM) well. The leaf vein structure of leaves was analyzed by leaf specimen scanning and microstructure measurements. Fluorescence labeling experiments were used to study the influence of leaf vein structure on moisture transport, and the geometric characteristics were obtained. A CBM extraction physical simulation experiment was carried out in a custom‐made experimental system. The temporal and spatial evolution of seepage‐temperature fields in reservoir during CBM recovery were studied, and the influence of leaf vein geometric characteristics and how they affected was analyzed. The results indicated that in experimental gas extraction, asymmetrically distributed branch wells improved the CBM recovery 4.02% higher than symmetric structure after 1000 seconds. The reduction in branch well angle leads to the decrease in gas pressure relief. If the branch well angle is reduced by 20°, it reduced by 11.34% after 4000 seconds. When the branch well length increased by 50%, it increased by 28.37%. Coalbed methane recovery effect can be improved by 6.81%, when the distance between branch wells increased by 50%. In the early extraction stage, the reduction in methane pressure and reservoir temperature was positively correlated with the initial methane pressure, but they were less affected in the later stage.

Coalbed methane extraction in multibranch horizontal wells: evolutions of reservoir characteristics with different geometric parameters

ABSTRACT Despite effective application of multibranch horizontal wells (MBHW) in the development of coalbed methane (CBM) fields, fewer studies have explored the variation of coal reservoir parameters under MBHW CBM extraction with different geometric parameters, which markedly restricts the maximum MBHW productivity. This study aims to develop a thermal–hydraulic–mechanical (THM)-coupled model, including coal deformation, gas migration, and thermal transport. Using the finite element simulation software, COMSOL Multiphysics, we analyzed the main geometric parameters of MBHW, including branch structure, branch angle, branch length, and branch quantity on the reservoir pressure, gas production, and reservoir temperature. In the entire CBM extraction process, the reservoir pressure and temperature at various points in the coal seam declined gradually; the closer to the wellbore, the faster the decline of the gas pressure and temperature in the coal seam. Typically, the cumulative gas production proportionally increases with an increase of branch length. The impact of the branch quantity on the productivity of unit length wellbore correlated with the extraction time. When the extraction time was relatively short (within 500 days), the gas production rate unit length of the wellbore increased gradually with an increase of the branch quantity.

CBM recovery technology characterized by docking ground multi-branch horizontal wells with underground boreholes

ABSTRACT Although ground multi-branch horizontal wells can maximally connect the fractures in a coal reservoir and greatly increase the single well yield, this type of well is not appropriate in many mining areas in China, since conventional drainage and recovery must be carried out on the ground. In this work, a new coalbed methane (CBM) recovery technology is proposed, which is characterized by docking ground multi-branch horizontal wells with underground boreholes. In addition, three specific docking schemes are also given. In order to improve the efficiency of CBM recovery and avoid the huge investment of purchasing ground drainage and recovery equipment in LiuLin Block, an engineering test for connecting ground multi-branch horizontal wells with underground boreholes was carried out at the 24307 working face of the Shaqu coal mine. The engineering practice has proven that the CBM recovery technology characterized by docking ground multi-branch horizontal wells with underground boreholes captures CBM more efficiently than conventional underground CBM recovery, and it enables underground drainage and recovery when compared to conventional ground CBM recovery, thus avoiding the huge investment in purchasing ground drainage and recovery equipment, and increasing economic efficiency as well as improving the applicability of horizontal multi-branch horizontal wells.

Technology Focus: Multilateral and Complex-Trajectory Wells (May 2019)

Technology Focus When students ask me about the most important way to maximize recovery, my answer is long directional wells. These wells have revolutionized the oil industry and are drilled under conditions never imaginable years ago. One outstanding example is the Troll field in Norway. The field consists of large, very thin reservoirs, down to 30 ft thick, which are drained by multibranch horizontal wells with horizontal departures approaching 18,000 ft. Not only have many drilling challenges been overcome, but also, from a production perspective, the wells are equipped with intelligent technology such as autonomous gas stop to maintain the pressure drive for the oil. Initially of no commercial interest because of a lack of technology, this field has been a very important driver for the current state of the art for long horizontal wells. Troll has been Norway’s largest oil producer in recent years. This has been made possible by the development of long-horizontal-well technology. The oil industry is currently undergoing a technological transformation that will add value, improve processes, and reduce cost. Future drilling engineers will have knowledge of robotics, automation, and organizational efficiency, which is highly appealing for recruitment. A prerequisite for this step change is the industry’s high level of technology. The selected papers address various aspects of horizontal wells. A field case of how to plan and drill through highly depleted reservoirs is given in paper OTC 28517. Three depleted zones must be penetrated before drilling into the untapped reservoir with a low drilling margin. This is a good example of drilling an extended-reach well using an integrated approach between various disciplines. Another example is given in paper SPE 191436, which shows how a complex U-shaped well path from old wells can be used to obtain good reservoir exposure to drain depleted wells further. Equipment is continuously improved, and paper SPE 189947 presents new ultrasonic technology to evaluate the state of multilateral junctions. SPE 191271 Extended-Reach Wells in Unconsolidated Sands in Bolivia by Gabriel Dordoni, Pluspetrol Bolivia OTC 28971 Correlation of Numerical Simulation and Digital-Image-Correlation Strain Measurements for a Multilateral Junction While Subjected to High Internal Pressure by Aihua Liang, Halliburton, et al. SPE 192672 Wireline Tractor Conveyance—A Technology Game Changer for the Gulf of Thailand by Sarunya Jongnarungsin, Mubadala Petroleum, et al.

Numerical study of multi-branch horizontal well coalbed methane extraction

ABSTRACTAlthough multi-branch horizontal well coalbed methane (CMB) extraction has been comprehensively investigated, fewer scholars have taken the effect of temperature into account, which brought a large deviation for the study of multi-branch horizontal well parameter design. In this work, the hydraulic-mechanical-thermal coupled model of multi-branch horizontal well CMB extraction was established. In order to verify the accuracy of the model and study the effect of temperature on CMB extraction, a series of numerical simulations based on engineering geological conditions and drilling arrangement parameters of 24307 face of Shaqu Mine were made, results show that: The CH4 production rate of both field data and numerical simulation result have the same changing tendency, and the difference between the simulation result and the actual value is not big. In multi-branch horizontal well CMB extraction process, the matrix shrinkage caused by temperature reduction and methane desorption dominates, the permeability continues to increase. Due to the effect of temperature on the amount of gas adsorbed by coal, the CH4 production decreases with the increase of initial reservoir temperature, and the permeability of coalbed increases with the increase of temperature.