Types Of Wells Research Articles

Analytical solution of capture time to a partially penetrating well in a semi-infinite aquifer

Calculating the capture time of contaminant to a well is important in the context of both groundwater protection and aquifer remediation. Although partially penetrating wells are much more commonly used than fully penetrating wells, there is no analytical solution for capture time calculations, probably due to the challenges of mathematically modeling such types of wells. In this study, an analytical solution of capture time was developed, based on the assumption that a partially penetrating well was installed in a homogeneous and semi-infinite aquifer. For an example case, the capture time result by the analytical solution fitted well with result by a high-resolution particle tracking method established according to the fourth-order Runge-Kutta algorithm. The impacts of different parameters are analyzed, and results indicate that the effects of both screen length L and anisotropic ratio a2 on capture time T are spatially dependent. Such comparisons also demonstrate that the influence of the lower boundary is stronger as penetration increases. In the end we compare the analytical solution for a line sink with that for a point sink, and demonstrate that larger differences occur near the wellbore, however, at a sufficiently large distance from the wellbore, the capture time distributions become the same for both source types.

Landfill Gas Flow: Collection by Horizontal Wells

Collection of landfill gas by horizontal perforated wells is studied. The problem combines flow through porous media in the landfill and unobstructed pipe flow in the well. Respective analytical solutions to flow equations are used in an iterative numerical procedure to solve the coupled system. Realistic landfill input parameters confirm the feasibility of estimates obtained with the model. The study identifies flow control parameters and furnishes tools to evaluate surface flux and radius of influence for this type of well.

RUNNING AND CEMENTING CASING FOR VERY LONG HORIZONTAL WELLS

Considering the geological and reservoir conditions in the north-west fields of Cuba, a program is being developed for casing running and cementing long extended reach wells with a horizontal displacement up to 10,000 meters. The paper reveals the result of the main tasks, which include design of the well construction, calculation of casing strings, development onting program, focused on obtaining a high-quality cemf a cemeenting in this type of wells. It also assesses the impact of the implementation of several proposed strategies, in the main indicators of the process of casing running and cementing. The design of our horizontal well profile considers that the profile is in second dimension because azimuth does not suffer variations and consists of five sections: first section is vertical, then two sections with angle construction and finally a horizontal section. To make the necessary calculations of our profile, it was necessary to develop a new calculation methodology that considers the initial and final data of the classical methodology and at the same time considers the new geometric condition. Considering the characteristics of geological formations and using the classical methodology for calculating the necessary diameters of casing strings and bits in construction are included: Conductor Pipe; Surface Casing; Intermediate Casing 1; Intermediate Casing 2 (Running in the hole in 2 stages); Production Liner - Liner and Slotted Liner Filter. Cementing program of conductor pipe and a surface casing using a stinger is developed, also the development program for running and cementing multistage sections for the first intermediate column, in addition the development program for running and cementing of second section in the second technical column.

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.

Analysis of Transient Flow to an Extended Fully Penetrating Well at Constant-Head Pumping.

Vertical wells with radial extension at the well bottom can improve the rate of water production. No study has yet investigated the effects of the transient state and anisotropy in directional hydraulic conductivities on the wellbore flux rate for this type of well. This study derives a semianalytical transient drawdown solution for constant-head pumping at a fully penetrating well radially extended at the bottom of a confined, anisotropic aquifer by applying Laplace transform and separation of variables as well as conducting a Fourier analysis. The results of this new solution indicate that transient and steady-state wellbore flux rates can be increased by a factor of two for greater radial extension of the well. Compared with an isotropic aquifer (a ratio of vertical and horizontal hydraulic conductivities equal to one), an anisotropic aquifer with the ratio less than one may produce a higher transient wellbore flux rate and lower steady-state wellbore flux rate. Moreover, the time required to achieve the steady-state wellbore flux rate can be substantially affected by anisotropy of the aquifer.

Groundwater flow to a general well configuration in an unconfined aquifer overlying a fractured bedrock

Unconfined aquifers sometimes overlie fractured bedrocks, consisting of unconfined-fractured aquifer systems. Pumping induced hydrodynamics in such aquifer systems has not received much attention as in other types of aquifer systems. This paper aims to obtain semi-analytical solutions of flow to a general well configuration in such an unconfined-fractured two-layer aquifer system. The examples of general well configuration, specifically discussed here, include: 1) a horizontal well, 2) a vertical well, 3) a vertical well with one horizontal collector, and 4) a vertical well with two horizontal collectors which are perpendicular with each other. The methodology is general and can be extended to other types of wells with minor modifications of solutions developed in this study. The point sink/source solution is first obtained using double infinite Fourier and Laplace transformations (where sink is for pumping and source is for injection). The line sink/source solution is then obtained via integrating the point sink/source along the desired direction and following the principle of superposition. The de Hoog numerical inverse Laplace transform and Gaussian Quadrature are used to obtain time-domain dimensionless drawdown solutions. The instantaneous drainage of water table and the inter-porosity flow of the underlying fractured aquifer are taken into account. The effects of the length of horizontal well on dimensionless drawdown and dimensionless drawdown derivative, and scaled sensitivity of the hydraulic parameters of the underlying fractured aquifer are explored. The dimensionless drawdowns and drawdown derivatives of a vertical pumping well, a vertical well with a single horizontal collector and a vertical well with two perpendicular horizontal collectors are also compared. The scaled sensitivity of dimensionless drawdown to the hydraulic parameters of the underlying fractured aquifer of these different pumping well structures is explored. The results of this study can be used to evaluate the hydraulic parameters using the drawdown data collected during a pumping test performed in a general well configuration in a unconfined-fractured two-layer aquifer system. Furthermore, the presented solutions can be utilized to design the pumping well to minimize drawdown in low-permeability or thin aquifers. By eliminating the inter-porosity flow term from the underlying fractured aquifer, the solutions are applicable to groundwater flow to a pumping well in leaky aquifers.

Experimental Investigation of CSS Assisted by Gas-viscosity Reducer Co-Injection with Different Types of Wells and Heavy Oil

The efficiency of conventional thermal recovery methods is limited due to heat loss, steam overlapping and other serious problems. Steam injection assisted by various additives, such as no-condensable gas, solvent and surfactant, has proved to be an effective and beneficial method to improve thermal oil recovery. However, based on literature review, few systematic and comprehensive explanation of the mechanism of the compound system of gas-chemical agent and the application criteria. In this paper, 3D physical experiments with different types of wells and heavy oil were conducted. The additives consist of nitrogen and viscosity reducer (VR). Different injection fluid combinations (single gas, single VR and gas-VR co-injection), fluid injection configurations (gas-steam and gas+steam, VR-steam and VR+steam,) were designed to study the effects of the compound system on oil recovery, oil-steam ratio and oil production rate. The results indicated that steam injection assisted by gas-VR performs well in enhancing the thermal recovery. Some conclusions are drawn according to the variation curves of characteristic parameters. The effects of the compound system still worked and increased the oil recovery after different injection patterns. Meanwhile, the cumulative SOR decreased to the different extent after the corresponding processes sequentially. The distribution of temperature showed that gas-VR co-injection not only inhibited steam overlapping, which promoted the horizontal expansion of the steam chamber but also reduced the viscosity of heavy oil significantly. More oil was produced due to the gas expansion energy. In summary, this work provides a practical understanding of CSS assisted by gas-VR co-injection and optimizing of the injection schemes for different types of reservoirs.

Calculation and analysis of dynamic drag and torque of horizontal well strings

In recent years, shale gas production horizontal well types mainly include conventional horizontal well, highly deviated well and scoop-shape horizontal well. For the sake of construction decision making, it is necessary to study these three types of wells from the aspects of drag and torque characteristic, weight on bit transferring efficiency, key hole sections or links and extreme penetration length. In this paper, these three types of horizontal wells were taken as the study objects. Their drag and torque, load transfer and extended reach drilling were explored based on the dynamic model of full hole drilling string and the simulation calculation of dynamic characteristics of full hole drilling string system. And the results were applied and tested on site in three shale gas wells (a conventional horizontal well, a highly deviated well and a scoop-shape horizontal well) in the Changning area, Sichuan Basin. And the following research results were obtained. First, the contact friction strength of the deeper part of the buildup section in the scoop-shape horizontal well is very high, and it is 1.67 times that of the hold section. The total contact force of buildup section in the scoop-shape horizontal well is 1.62 times that in the highly deviated well. Second, the contact friction strength of the hold section in highly deviated well is not only higher than that of its buildup section, but also higher than any characteristic section in the three well types of the same depth. Third, the operating stress of drilling strings during the drilling of three well types is not high, but during the extended reach drilling in the curved section of the scoop-shape horizontal well, it is necessary to focus on the twist off of drilling string in the hold section. Fourth, the weight on bit transferring efficiency of scoop-shape horizontal well is lower than that of conventional horizontal well and highly deviated well. In conclusion, the research results preliminarily reveal the drag and torque characteristics and active load transferring mechanisms of conventional horizontal well, highly deviated well and scoop-shape horizontal well for shale gas production, and present important hole sections for safety assessment. They can be used as references for efficient and safe construction of shale gas horizontal wells.

Assessment of Organochlorine Pesticides in Phreatic Aquifer of Pampean Region, Argentina.

This work evaluates the factors affecting the presence of organochlorine pesticides in Pampeano aquifer in the Quequén Grande River watershed, Buenos Aires Province, Argentina. Eighteen sampling sites were selected in order to have representatives of different type of wells and types of soil. Among the analyzed compounds, endosulfan showed the highest concentrations (4.75ng l- 1 mean), which could be related to use in the recent past. Others important pesticides groups detected were HCHs (1.1ng l- 1 mean) and heptachlors (2.17ng l- 1mean). The analysis of the results show that the thickness of the unsaturated zone is the main factor related to the concentrations of pesticides and there were no differences according to wells or soil types. Although agricultural use of most OCPs has been banned in Argentina from more than 30years ago, their residues are still detected in groundwater of the region, indicating their high persistence.

Hydrochemical processes, variability and natural background levels of Arsenic in groundwater of northeastern Mendoza, Argentina

Northeastern Mendoza is an arid area dominated by stabilized dunes and paleochannels. Groundwater is the main source of water for domestic and subsistence economy. Two types of wells are used for groundwater withdrawal. Wells operated by conventional windmills or pumps (Ws) and local traditional bucket wells operated manually (BWs). These wells are drugged a few cm below the water table, normally with a diameter of 1 m, remain always open and are located near corrals. The aim of this study was to evaluate the processes that control As in groundwater used As drinking water by rural communities. The study approach included an assessment of the natural as background levels and the use of environmental isotopes (δ18O and δ2H) to determine the origin of groundwater and improve the conceptual model for groundwater flow. Significant statistical differences were found between the chemical features of groundwater from Ws and BWs. The conceptual hydrogeologic model supported by isotopic data indicated that groundwater recharge was from the main Mendoza/Tunuyan Rivers in remote areas and that local rainwater recharge is negligible. The isotopic data suggests that a faster groundwater flow recharge could occur without any influence of a previous evaporation process. The natural As background level was 104 µg/L, with a range of between 8.6 and 394 µg/L. The average As concentration in Ws was 114 µg/L. Water from BWs showed higher average As concentration of 235 µg/L with a higher dispersion, high HCO3−, NO3− PO 4 −3 and Cl− concentrations, and the lowest concentrations of O2 with greater turbidity than groundwater from Ws. The increase in As concentrations in groundwater of NE Mendoza is not related to evaporation processes despite arid climatic conditions. According to the oxidizing environment in the aquifer, high pH and very fine sediments, adsorption–desorption processes from solid surfaces were the determining factors for the availability and spatial variability of As in groundwater. Spatial variability was related to type of well rather than to geomorphologic units or to flow direction. The design of bucket wells, near corrals, allows the input of windblown sediments and leachate from livestock units creating point sources of As contamination in water used for human consumption.

Research of Dynamic Reserves Estimation Methods for Complex Gas Wells in Low Permeability and Tight Gas Reservoir

As material basis of compiling and adjusting developing scheme, dynamic reserves are crucial for predicting well spacing density and stable production potential. Currently, for conventional gas wells with good physical properties and abundant pressure test data, the main evaluation methods of dynamic reserves are ranging from material balance equation to flowing material balance. However, complex gas wells in Ordos Basin such as type of inadequate pressure test data in low permeability reservoir, water production, downhole throttling in tight gas reservoir, these three types of wells cannot be easily applied to the current evaluation methods. Therefore, this paper presents rapid methods for estimating dynamic reserves in complicated situations which are based on analysis of gas wells percolation and production. The key points of new methods are evaluation of the formation pressure without shutting well, visual pressure drop and water influx, pseudo-pressure regularization rate under superposition time function respectively. Finally, with applying methods to track and evaluate the dynamic reserves of M gas field in Ordos Basin, results show that approaches are accurate and evaluation periods are greatly shortened. Besides, the procedures are simple which can be implemented in desktop application or spreadsheet with minimal computational effort.The new methods provide a direct reference for the deployment of gas infilling wells and gas wells refracturing, and further improve the utilization level of reserves.

A comparison of the efficiency of riverbank filtration treatments in different types of wells

Abstract In the paper, a comparison of the efficiency of riverbank treatments is outlined for the Krajkowo well field, where different methods of water abstraction are used. The water is extracted from 29 vertical wells that are located at a distance of 60–80 m from the channel of the River Warta and from a horizontal well with radial drains located 5 m below the bottom of the river. The results of a two-year water-quality investigation indicate that the water quality in both types of abstraction system is influenced by the quality of river water. The water quality observed in the horizontal well is closely similar to that of the river water, with similar concentrations of sulphates, nitrates and micropollutants, but a reduction in bacteriological contamination and plankton is clearly seen. The reduction in contaminants is mainly the result of physical processes, such as mechanical entrapment of suspended material and colloids as well as bacteria and plankton. In the vertical wells, the influence of contamination from river water is also visible, but the reduction in contamination is more significant, especially in cases of bacteria, plankton, micropollutants and nitrates, and is determined by both physical and chemical processes, such as sorption, dissolution, red-ox processes and denitrification. The present research shows that river water treatment is more effective in the case of vertical wells. The most favourable distance of a well from the channel of the river, from the perspective of water quality, is 150–200 m, which corresponds to a residence time of about six months.

Does type of well drilling matter for local governments' fund balances?

The purpose of this study is to examine whether the type of wells drilling in Pennsylvania matters to the fund balance of local governments in Pennsylvania. After conducting one‐way analysis of variance and Kruskal–Wallis equality‐of‐populations rank test, the median value of fund balance of local governments have differences by the type of wells drilling. This result can suggest that the local governments of Pennsylvania should consider how to levy the level of impact fee to the companies operating wells for extracting shale gas. In other words, it should be designed more systemically by the type of wells drilling in Pennsylvania.

Saving for a dry day: investigating well ownership and watering practices during droughts

ABSTRACTGrowing demands for irrigation water are tapping groundwater supplies beyond their natural rates of replenishment, which has profound implications for sustaining communities in semiarid regions. This paper investigates the drought-time watering practices of Kansas well owners, a key social group whose water consumption is pivotal to prolonging groundwater formations. I address two questions: Do well owners and non-well owners have different responses to droughts? Is the relationship between water supply awareness and water conservation during droughts moderated by water supply infrastructure? To answer these questions, I constructed one of the only datasets of well owners used in the social sciences by surveying well owners and non-well owners throughout Kansas (n = 864). My findings reveal that well ownership is significantly correlated to increased watering during droughts and water conservation varies among those who own different types of wells. Furthermore, increased levels of water literacy are negatively associated with water conservation during droughts. These findings support the Conservation of Resources theory, which holds that individuals stockpile their resources during non-stressful times and draw from their reserves during times of scarcity. Therefore, aquifer stewardship involves selective timing for making groundwater extractions.

Effects of vertical center well and side well on hydrate exploitation by depressurization and combination method with wellbore heating

The effects of depressurization and the combination method with wellbore heating on vertical center well and vertical side well on hydrate exploitation were investigated and compared in this study. Six combinations of experimental groups were conducted using different exploitation methods (i.e., depressurization and the combination method) and different types of wells (i.e., vertical center well and vertical double-side wells). The results show that the lower the production pressure is, the better it can generate hydrate productions. Meanwhile, it is further confirmed that the heating process can greatly increase the gas production rate of hydrates. In addition, when using depressurization within a certain exploitation range, the location of the production well has little impact on the effects of hydrate exploitation. However, with double-side wells using the combination method, the effect of driving force in hydrate decomposition is weakened due to the larger heat loss. Therefore, when the heating well is located close to the boundary of the hydrate deposit, the use of double-side wells is less productive than that of a center well. As a result, when using the depressurization method, the location of the production well within the exploitation zone should be as close to the coastal line as possible with a stable hydrate deposit layer. On the other hand, when wellbore heating is applied, it is suggested that the heating well should be arranged near the center of the hydrate deposit. Furthermore, it is found that there is a right-skewed bell curve shape relationship between the exploitation time and the energy generation level using the combination method.

Finite service life evaluation method of production casing for sour-gas wells

The material selection and design for oil and gas wells containing hydrogen sulfide and carbon dioxide is very difficult due to the uncertainties such as the changeable production capacity, partial pressure of corrosive medium (like CO2 and H2S). For oil and gas wells, there is a high production rate in the initial stage while the production rate is very low in the rest of stage. Meanwhile, some wells may have water outflow in the very early period but they even become flooded in the following process. According to relevant standards, Nickel-based alloys must be used in these conditions. However, using Nickel-based alloys could greatly increase construction cost. In this paper, we propose an evaluation method for those types of wells based on a finite life design theory, which utilizes a high pressure high temperature (HPHT) flow corrosion test. Furthermore, phase state and transformation kinetics are introduced into the evaluation. The simulation covers the formation of water corrosion in three periods, which include the condensate water gas production period, the water-carrying gas production period and the water accumulation period. Corroded casing strength was derived according to API Specification 5CT, and the residual strength including residual tensile strength, residual internal pressure, and the residual collapsing strength of the casing. Finally, residual strength data was used for the finite life theory based on the resistance safety method, and compared with the Offshore Drilling Manual, the finite service life can be predicted.

HYDROCHEMICAL CHARACTERISTICS OF THE GROUNDWATERS IN PRILEP’S PART OF PELAGONIA VALLEY – REPUBLIC OF MACEDONIA

This paper presents the results of hydrochemical investigations of groundwater from the Prilep part of the Pelagonia valley - Republic of Macedonia. These investigations were carried out by analyzing 12 samples of groundwater, taken from the exploitation wells. Samples are taken once a season, during August 2013. Values of the pH were determined with the field digital pH meter, while cations are determined by inductively coupled plasma-atomic emission spectrometry (ICP – AES). For the determination of the anions are used standard EPA methods (gravimetric - TDS, volumetric - Cl-, spectrophotometric - NO3-, NO2-, NH4+ and turbidimetric - SO42- with the spectrophotometer 6715 UV / VIS, Jenway). Тhe maps with spatial distribution of the hydrochemical components were prepared using the IDW (Inwerse Distance Weighting) method for map generation (Geographic Information System software (GIS) ESRI® ArcGis™ 9.2 and its extension Geostatistical Analyst). Spatial distribution maps were constructed according to the coordinates and sample content of each analyzed sample. Samples were taken from the wells which are divided into 3 groups: wells with free level with depth up to 10 m, wells with free level with depth up to 100 m and artesian wells. The graphical methods, Piper diagram and Chadha’s diagram, were applied in order to determine the hydrochemical properties of the groundwater. The results indicate that the groundwater samples have different hydrochemical properties. Ca 2+ >Na+>Mg2+ for the cations and HCO3- >Cl- >SO42- for the anions were dominantly dissolved ions in the majority of the water samples. Generally, increased values of Ca2+, Mg2+, Na+, K+, HCO3-, K+ and Cl- occur in the groundwater from deeper artesian wells, as a result of the longer retention time of water in the underground and its interaction with the geological environment. Dominant groundwater in Prilep field, in all three types of wells, are waters from hydrocarbonate class (HCO3¯), calcium group (Ca), the first type of water. Groundwater from the shallow wells show the increasing content of K+, NO3- and PO43-which indicates water pollution from fertilization of the cultivated areas, livestock farms as well as communal wastewater. Although hydrochemical data are obtained on the basis of water samples taken only once, they provide an indicative insight into the hydrochemical composition of the water. To obtain more reliable data, taking groundwater samples from wells should be performed multiple times in different seasons.

The Halladale–Speculant fields: the first nearshore gas fields to be developed from mainland Australia

Extended-reach drilling (ERD) is becoming an increasingly common technique used to explore for hydrocarbons and develop fields in areas where simple vertical wells cannot be drilled due to access problems, stakeholder concerns, environmental issues, poor reservoir quality and/or cost. While these types of wells are generally more expensive and technically challenging to drill than vertical wells, they can be very cost-effective, and if a discovery is made, considerably quicker to monetise when future development costs are also taken into consideration, particularly in offshore environments. In 2014–2015, the conventional Exploration and Production division of Origin Energy (now Lattice Energy) drilled three onshore-to-offshore ERD wells and a geological sidetrack in the Otway Basin with horizontal offsets of 1929, 2576, 4239 and 5152 m targeting an undeveloped gas field (Halladale) and exploration prospect (Speculant) located in Victorian state waters near Port Campbell. The three wells (Halladale-2, Speculant-1 and Speculant-2) and sidetrack (Speculant-2ST1) were drilled during a single drilling campaign from the same pad to reduce mobilisation, drilling and development costs. Halladale-2 was designed to develop the Halladale Field, while Speculant-1, -2 and -2ST1 were designed to evaluate the Speculant Prospect. Both Speculant wells and the sidetrack encountered significant gas columns with Speculant-1 and Speculant-2ST1 subsequently completed as producers after being successfully flow tested. A 33 km onshore pipeline was then constructed to transport the gas from Halladale and Speculant back to the Otway Gas Plant (OGP) for processing and sale. The arrival of first gas at the OGP from the Halladale and Speculant gas fields on 26 August 2016 marked a significant milestone for Origin Energy in terms of accelerated project delivery. It also represented the end of a 15-year journey for Halladale from exploration to discovery to development. The drilling campaign also set several records in the process with: (1) Speculant being the first offshore field to be discovered from mainland Australia; (2) Halladale and Speculant being the first offshore fields to produce gas back to mainland Australia from onshore wells; (3) Halladale-2, Speculant-1 and Speculant-2 being the three longest onshore-to-offshore wells drilled to date in Australia (in horizontal departure terms); and (4) Halladale-2 being the longest well (in mMDRT terms) drilled to date in the Otway Basin. Speculant is a good example of how transition zone (TZ) seismic and ERD technology can be used successfully to explore and develop resources in areas previously considered too difficult by using more conventional seismic acquisition and drilling technology.

Application of integrated rock typing and flow units identification methods for an Iranian carbonate reservoir

During the exploration phase of any oil and gas field, recognition of borehole type, its completion approach, and understanding of the future reservoir performance are directly interrelated to identification of the reservoir's rock types and flow units. Identifying different geological events, lithofacies characteristics, diagenetic processes, and level of heterogeneity can be the first step for knowing rock types and consequently flow units in its reservoir layers. These result in an acceptable dynamic model of a field development and relatively reliable production forecasts.Focus of this paper is on rock typing and flow unit classification for a carbonate reservoir of a green field. Four petrophysical methods including Rock Fabric Number (RFN), Winland porosity-permeability plot (R35), Reservoir Quality Index/Flow Zone Indicator (RQI/FZI), and Bulk Volume Water (BVW) were implemented on four exploration wells. At the next step graphical tools (Stratigraphic Modified Lorenz Plot (SMLP), Modified Lorenz Plot (MLP) and Stratigraphic Flow Profile (SFP) were used to locate established flow units and rock types within the reservoir column. Lastly, variation and frequency of defined flow units have been used to achieve a satisfactory understanding of the level of heterogeneity and the possible effect on well production.Integration of defined flow units by different methods inferred a high level of heterogeneity in the studied reservoir and the BVW was chosen as the best method of rock typing for feeding to the static model. The BVW method assists in considering main variation of reservoir properties meanwhile avoid complexity of models. During modelling, choosing an optimum number of rock types for fine-grid model with small dimensions cells (50 m*50 m*1 m) can help to separate different layers vertically without necessity of dividing them to many distinct subzones. Usually, groping numerous subzones during up scaling is confusing and complicate; likewise, in a coarse grid may omit or mix some frequency of thin seal and productive subintervals in reservoir zones. Comparing achieved flow unit classification with outcomes of production test showed in this reservoir with high level of heterogeneity an adequate type of well is vertical and highly deviated ones, moreover, dual completion can be the best type of production which separate high and low productive zones.

Limit Drainage Radius for Different Types of Wells in a Shale Reservoir

The low porosity and permeability of shale deposits is due to the complex structure of the pores. Due to the threshold pressure gradient, fluid seepage in low-permeable reservoirs does not obey Darcy’s law. Horizontal well drilling and fracturing treatment are effective methods of developing lowpermeable reservoirs, since these methods increase the well drainage area. In the present study a mathematical model of gas flow in different types of wells is obtained on the basis of seepage theory. The pressure distribution and relationship between the threshold pressure gradient and limit well spacing are obtained using the point-source function and Laplace transforms. The limit well spacing increases with decreasing threshold pressure gradient. The method is of importance for determining an appropriate spacing between different combinations of different types of wells in the development of shale gas.