A numerical simulation study using the CMG-STAR Simulator was performed to compare the performance of the newly developed process (VWSAGD) uti- lizing verticalwells to enhance heavy oil recovery during steam assisted gravi- ty drainage against the conventional steam assisted gravity drainage process which utilized horizontal wells (HWSAGD) under the same operating condi- tions. Two identical reservoir models were simulated for the two processes using 3-Dimensional, black heavy oil model (14˚ API). Each reservoir type consists of 49 × 49 × 20 grid blocks on a 5-acre model, which incorporated a typical heavy oil reservoir rock and fluid properties taken from the SPE case study, stspe001.dat (CMG 2015 release). A sensitivity analysis for both processes was performed for the grid density, soaking time, steam quality, bottom hole producing pressure, steam injection rate, reservoir thickness, re- servoir area, and horizontal to vertical permeability anisotropy. More prefera- ble reservoir conditions are those such as high horizontal to vertical permea- bility ratio, thick reservoir oil zones, as well as improved reservoir recovery for the VWSAGD process. Under unfavorable conditions such as thin reservoir oil zones, an improved reservoir recovery response was limited for the VWSAGD process and could be uneconomical in real field cases. Finally, the simulation results from this study include cumulative recoveries, Steam oil ra- tios, produced water-oil ratios, pressure and temperature distributions, and production rates. In addition, the results from this study have shown that the new VWSAGD process is more favorable than the conventional HWSAGD process.
Abstract: In oil and gas production, developing bottom-water reservoirs with active aquifer requires production strategy that can handle production-rate-sensitive phenomenon – water coning. The coned water that moves into the completion interval results in production related problems: excessive water production, surface water handling, low oil productivity, among others. To this end, several correlations: critical rate, breakthrough time and water-cut performance after breakthrough have been developed based on analytical, empirical and numerical approach to evaluate water coning tendencies in petroleum reservoirs. Some of the developed correlations have gained field application. However, limited literatures are available that have evaluated the prediction of these water coning correlations. Thus, the various water coning correlations for vertical well were evaluated and the obtained results show that most correlations have the same prediction profile. Conversely, these correlations predicted different coning parameters’ value. Further analysis of the results depicts that critical production rate and breakthrough time in verticalwells are indirectly dependent on fractional well penetration. In addition, the correlations developed from water-cut data for the prediction of water-cut performance after breakthrough indicate more realistic predictions in the water-cut profile than the correlations developed from water-oil ratio. Therefore, to delay water coning tendency in bottom-water reservoirs, fractional well penetration is a consideration in verticalwells to establish optimum critical oil rate and breakthrough time during oil and gas production.
A novel process utilizing verticalwells to enhance heavy oil recovery during steam assisted gravity drainage has been developed. In the vertical well steam assisted gravity drainage (VWSAGD) process shown in Figure 1, the vertical well includes two production strings which are separated by three packers (one dual and two single packers): the short injection string (SIS) is attached to the bottom of the annulus and completed in the top quarter of the perfo- rated formation, while the long production string (LPS) is attached to the bottom of the production tubing and completed in the bottom quarter of the perforated formation. The new process (VWSAGD) requires an initial start- up period (warm-up stage) where the steam is injected into both of the injec- tion strings and production string for a specified period of time of about 14-30 days; then both strings are closed to injection for a specified time period of approximately 7 - 10 days (soaking period). After the initial warm-up and the soaking period, the long production string is opened for production, and the short injection string is opened to continuous steam injection for the rest of the specified simulation time. A commercial simulator (CMG-STAR Simula- tor) was used to study the performance of the new VWSAGD process. A sen- sitivity analysis was performed for the grid density, soaking time, steam qual- ity, bottom hole producing pressure, steam injection rate, reservoir thickness, reservoir area, and horizontal to vertical permeability anisotropy. The results of this study have shown that the new VWSAGD process is more preferable for reservoir conditions such as high horizontal to vertical permeability ratio and thick reservoir oil zones.
zone, and moving up the wellbore to repeat this process at next desired productive interval . Many authors have studied the performance of verticalwells with vertical fractures [5-7]. However, the performance model of verticalwells with horizontal fractures has been investigated occasionally, and most studies focus on numerical solutions. W. Sung (1987) compared the performance of producers with vertical and horizontal fractures by numerical reservoir simulation , and Peter Valko (1998) studied the transient behavior of finite conductivity horizontal fractures ; Lasen Leif (2011) studied the pressure in multilayer reservoirs influenced by horizontal fractures . However, few studies have been devoted to an analytical solution for the productivity of verticalwells with horizontal fractures considering oil-water two-phase flow in regular waterflooding patterns. In this paper, an accurate productivity model for verticalwells with horizontal fractures is proposed in conjunction with threshold pressure, material balance, and pressure superposition, for the sake of making better engineering decisions about the development of the reservoirs with complex hydraulic fracturing.
The original pressure governing model for elliptical flow introduced by Tiab (1994) involves the drainage area, which may affect the calculations if the pressure test is too short for the development of the late pseudosteady-state period. An experienced user of the TDS technique may deal with that problem using the point of intersection between the radial flow and the birradial flow regime lines, Tiab (1994). However, to overcome this problem, Escobar, Bonilla and Ghisays-Ruiz (2014) formulated a new elliptical/birradial flow model for verticalwells in either fractured or unfractured formations.
The level of pressure gradient needed to enable fluid to overcome the viscous forces and start flowing is referred to as the threshold pressure gradient, TPG, or minimum pressure gradient required for fluid flow. While it has been observed that TPG has an important effect on the pseudorradial flow regime of a fractured vertical well, the early linear flow regime caused by the fracture is not impacted by TPG. In this work, TDS methodology is implemented for interpretation of pressure tests in uniform-flux fractured verticalwells of low permeability reservoirs affected by TPG. Two governing equations of the TPG effect on pressure response were developed, in addition to two correlations, which were all tested and validated in a synthetic case.
From the well testing point of view a homogeneous variation of the permeability is accounted by the permeability modulus which was introduced by Pedrosa (1986) and defined by Equation (10). Since then, several researchers have been presented. Escobar, Urazan and Trujillo (2018) recent presented a methodology for well test pressure interpretation in stress sensitive formations drained by horizontal wells. They did a good review of existing literature. Escobar et al (1996) studied the effect of the poisson ratio and the young modulus on well pressure behavior. Duan et al (1998) performed a sensitive analysis by numerical simulation and lab tests to study the influence of stress on naturally fractured parameters. They concluded that the sensitivities are generated mainly by the network of fractures.
It is important to however note that the sustainable extraction rates, on a long term basis, may be impacted by the presence of entrapped residual saturation, held for example by capillary action, adsorption kinetics, or by sequestration of contaminants due to sorption and partitioning. Cagle et al. (1997) reported the results of a case study in which the objective was to extract jet fuel from clay soils at the Naval Air Facility, El Centro, California. The authors used fluid injection with vacuum extraction (FIVE) as an alternative method of treating the site soils without disrupting the existing fuel farm’s operation. They recommended a combination of approaches including multiphase extraction, air injection/pneumatic soil fracturing, and bioremediation. It is of interest to note that in Cagle’s et al study, the rate of hydrocarbon biodegradation was estimated to range from 1.6 to 39 mg/kg/day. In the case of the WIDE active approach, a step of bioventing/air extraction process may be needed to address the residual phase. As site conditions change, whereby some of the residual phase contaminants are released (as may be evident from re-appearance of free product in wells), the active extraction process can then be re-implemented.
In this research study, several simulation runs were made in order to investigate the effects of well and reservoir parameters on the the time to reach abandonment conditions for both horizontal and verticalwells in retrograde gas-condensate reservoirs. An attempt will be made to obtain a relationship between well and reservoir parameters and the time to reach abandonment conditions for both horizontal and verticalwells. In this research, the abandonment condition for both horizontal and verticalwells is reached when the well production rate becomes less than 100 MSCF/D for a bottom-hole flowing pressure of 700 psia.
The objective of this paper is to evaluate the additional oil recovery in which recovery processes considered include water injection and drilling horizontal and verticalwells in a depleted sandstone oil reservoir in which a reservoir model (GEM) was developed using history matching with field production data in order to verify the model results. It is effective for modelling any type of reservoir where the importance of the fluid composition and their interactions are essential to the understanding of the recovery process. The study will not explain the effect of reducing CO 2 emission and
Abstract: Developing giant new and mature oil fields by horizontal drilling is one of the most valuable technologies employed nowadays since it can maximize mature field's benefits. Horizontal wells are offering multiple advantages including, higher production rates, better drainage, lower drawdown and delay water production. In addition, especially in offshore fields, horizontal wells compromise the ability to drill more multi-lateral wells from a single platform enhancing ultimate recovery because of reaching the bypassed oil buckets away from the offshore jackets reducing the number of verticalwells and minimizing offshore infrastructures reducing costs and time. These technologies have been, and will become an attractive topic for more studies and investigations. Development of mature fields, could be included into three major categories (a) well engineering (b) surface facilities and (c) reservoir engineering. This paper focuses on the reservoir engineering aspects and mainly on applying horizontal wells in giant mature fields to maximize their oil recovery. Field maturity in both well engineering and surface facilities will be the subject of next papers. The results have shown that, applying horizontal well drilling in giant mature fields is very crucial because of the horizontal well production improving factor (PIF), which represents the improvement of horizontal well production compared with vertical well production at the same locations, has been significantly increased. Horizontal well production improving factor (PIF) has increased with time along the reservoir life from pre-mature (virgin) to mature phases. In this study, it has increased from 1.23 to 1.28 during the last 9 years (2004-2012). However, simulation prediction results for next 9 years (2013-2021) have shown that, PIF has reached almost 5. That is because the oil column thickness become more thinner due to water movement through moving up toward the water oil contact and through high permeability streaks. As field practice, using pilot holes during drilling new infill and/or re-entry horizontal wells in mature oil fields is essential for successful high potential horizontal wells.
Horizontal wells have been applied all over the world because of their high productivity. The well performance of these wells has not been well-defined yet. Therefore, the main objectives of this study are to evaluate the well performance of horizontal wells and compare it to that one of verticalwells. Using the same drainage areas and similar fluid properties, the well productivity and Inflow Performance Relationship (IPR) for both vertical and horizontal wells are evaluated and compared for steady-state flow of compressible and incompressible fluids. Current models for both types of vertical and horizontal wells are evaluated to stress their strengths and weaknesses. The replacement ratio of horizontal well to vertical well are calculated. Furthermore, a sensitivity analysis is performed on common variables to compare and evaluate vertical and horizontal well flow equations.
As demonstrated in previous studies, horizontal and slant wells have significant advantages over verticalwells in un- confined aquifers, and thus they were largely used in un- confined aquifers for pumping or drainage purposes. How- ever, none of above-mentioned studies considered the effects of unsaturated processes on groundwater flow to horizontal and slant wells in unconfined aquifers. In the case of flow to verticalwells in saturated zones, the effects of unsatu- rated processes have been investigated by several researchers (Kroszynski and Dagan, 1975; Mathias and Butler, 2006; Tartakovsky and Neuman, 2007; Mishra and Neuman, 2010, 2011). For example, Tartakovsky and Neuman (2007) con- sidered axisymmetric unsaturated–saturated flow for a pump- ing test in an unconfined aquifer and employed one param- eter that characterized both the water content and the hy- draulic conductivity as functions of the pressure head, assum- ing an infinite thickness of the unsaturated zone. Mishra and Neuman (2010, 2011) extended the solution of Tartakovsky and Neuman (2007) using four parameters to represent the unsaturated zone properties and considered a finite thickness of the unsaturated zone (Mishra and Neuman, 2010) as well as the wellbore storage (Mishra and Neuman, 2011). The main results from the studies concerning verticalwells in- dicated that the unsaturated zone often had a major impact on the S-shaped drawdown curves.
Wells are separated by type (vertical, horizontal, or extended horizontal) using Noble’s well naming system or the number of hydraulic fracturing stages, if available. Directional and deviated wells are categorized as verticalwells for this study because of similar water require- ments. Horizontal wells are separated from extended ho- rizontal wells by Noble’s well naming system or the number of hydraulic fracturing stages used when avail- able. A horizontal well will typically be hydraulically fractured in 20 stages. Recently, Noble has drilled and hydraulically fractured longer horizontal wells that can include over 40 stages to hydraulically fracture. Hori- zontal wells that require over 25 hydraulic fracturing stages are defined as extended horizontal wells in this study.
Abstract: Numerous studies have been carried out on Formation damage in verticalwells but less investigation was conducted in horizontal wells, this, therefore necessitates development of an approximate filtration theory through a compressible cake medium. A mathematical model was developed to describe the mechanisms and processes of filtration into the Formation through a compressible filter cake during drilling of horizontal wells. Goodman’s integration technique was adopted for the solution, taking into consideration the effects of non-linearity and gravity. The result shows that the Cake thickness buildup at different values of constant of non-linearity is very small, also, depth of invasion was observed to increase at the beginning of drilling and reduced as time went by. The rapid decline in Solid pressure indicates more damage in horizontal wells than other models used for verticalwells. An approximate analytical solution combining both the steady and transient components has been successfully applied to solve the filtration theory equation developed for horizontal wells. The model is easily applicable to estimate important values needed to know the status of the formation during the drilling of horizontal wells.
The aim of the work was to study the experience and effectiveness of applying various methods of gas drainage in the mining of a thick coal-seam 52 in the geological conditions of the Kotinskaya mine, Russia. The range of gas drainage methods used at the mine included: preliminary methane drainage (predrainage) of the working seam, drainage from the goaf by verticalwells drilled from the earth's surface; drainage from the goaf by horizontal wells drilled through the pillar from the roadway; drainage from the goaf using a main gas drainage pipeline, installed behind a brattice and connected to a gas-exhausting fan mounted on the earth's surface. During the work, the gas control equipment data and the longwall face productivity data were analyzed. As a result of the studies, the dynamics of the emitted gas of the longwall face was established, the dependences of gas content of the longwall face output were obtained, and the relative cost of various gas drainage methods was established. The conclusion is that the low efficiency of predrainage of the working seam. The scientific novelty of the work is to establish the influence between zones of geological dislocations and the speed of advance of the longwall face and the volume of emitted gas of the block.
Al(Ga)As/GaAs distributed Bragg reflectors (DBRs) for the long wavelength optical communications window. GaInNAs have potential cost advantages compared to indium phosphide (InP)-based approaches. It can be used to fabricate several devices, such as high performance laser diodes among which are vertical cavity surface emitting lasers (VCSELs) emitting in 1.3 µm window. The massive interest in VCSEL devices has focused on semiconductor optical amplifier (SOA) based VCSEL technology. Vertical cavity semiconductor optical amplifiers (VCSOAs) are important components in optical fiber networks. These devices have advantages over edge emitting lasers (EEL) and in plane- semiconductor optical amplifiers (SOAs) of various amplifier lengths. The vertical cavity geometry for such devices yields high coupling efficiency to optical fiber, which is useful for achieving a low noise figure with better performance. It also allows for single wavelength amplification, and two dimensional array fabrication; hence lowering the power consumption and manufacturing cost. The narrower bandwidth of the vertical cavity structures makes the devices also good for filtering applications (Piprek, Björlin and Bowers, 2001).
There are some scholars have pointed out that through surfactant injection technology, polymer enhanced foam flooding, high and low polymer concentra- tion alternating injection technology can effectively improve polymer flooding effect -, However, offshore oilfields are limited by the operating space of production platforms, and the implementation of new chemical flooding or oth- er improvement measures requires a greatly expand and reform of the produc- tion platforms, because of the high operating costs of offshore oilfields, it is very difficult to implement new chemical flooding or improvement measures. Rea- sonable optimization method of perforation position refers to the production wells and injection wells in one production unite, these wells adopt the same or different perforation position in the reservoir, so as to differentiation of injec- tion-production corresponding relations, and that was used to inhibit gravity differentiation or displacement phase breakthrough through. This method only needs to make corresponding decisions in the completion stage of production wells, and it does not need to expand and reform the production platform, nor does it need additional development investment, Therefore, under the condition polymer flooding, the research of reasonable perforation position can obtain the synergistic effect of the two methods, which can further improve the develop- ment situation of oil field, but also maintain higher economic benefits.
BZ Oilfield is a medium-sized oilfield with shallow delta facies deposits in Bohai Bay of China, compared with fluvial and delta facies oilfields, there is no mature experience for reference of reservoir configuration, well pattern arrangement and development model in offshore oilfields in China. In view of the difficulty in describing the reservoir configuration of shallow water delta, the single distributary sand dam in shallow water delta is characterized by well-seismic combination and multi-attribute constraints. The mathemat- ical mechanism model of pinch-out position of sand body is established, fine characterization of BZ shallow water delta reservoir is put forward. The hori- zontal well pattern arrangement type for shallow water delta reservoir is pro- posed and the method of well pattern optimization based on vertical dis- placement theory is put forward. A method of inversion of reservoir connec- tivity using production dynamic data by numerical well testing is proposed and a new method for optimizing water injection rate in water injection wells is proposed aiming at the difficulty of recognizing injection-production con- nectivity of shallow water delta reservoirs. The fine configuration of BZ shal- low water delta reservoir based on distributary sand dam is proposed, which guides the recognition of remaining oil distribution law. By deploying ad- justment wells, the water flooding coincidence degree of actual drilling is 86% compared with that of pre-drilling prediction, which indicates that the re- search results of reservoir configuration can effectively guide the under- standing of oilfield geology. Through the theoretical well arrangement type of vertical displacement of single sand body in horizontal wells of shallow water delta reservoir, a high water flooding recovery rate of 35% is achieved in pri- mary well pattern. The connectivity coefficients of injection-production boundary of shallow water delta reservoir configuration are calculated, and the water injection distribution coefficients are obtained by normalizing the