The field under study is structurally and stratigraphically complex, which increases the uncertainties associated with field development. To optimize reservoir characterization using seismic data, seismic inversion (Deterministic, Stochastic and Simultaneous) was planned to be performed using the 3D seismic data covering the field. Given that well log data provide constraints and calibration in the inversion workflow, their quality has a direct impact on the robustness of inversion results. This paper focuses on corrections made to sonic and density log data to make them suitable for seismic inversion.
Sonic and density logs have shallow depths of investigation and are affected by borehole irregularity and filtrate invasion. Errors due to borehole irregularity in the section overlying the reservoir impact two key stages of the inversion process: wavelet extraction using well-seismic ties, and construction of the low frequency or a priori model. Invasion within the reservoir impacts the accuracy of porosities obtained from seismic impedance data. Typically porosity estimation is done using a regression relationship between porosity and acoustic impedance derived from well log measurements. The log impedance data (both velocity and density) are affected by saturation changes related to filtrate invasion which must be corrected for, to obtain a reliable porosity-impedance relationship.
A robust and practical workflow to address log quality issues begins with log data quality QC: identifying zones with missing logs or borehole affected log readings. Shear sonic logs are unavailable for many wells, which limits their use for Simultaneous inversion, and for invasion correction using a rock physics model. We constructed shear sonic logs from compressional sonic logs using a rigorous, iterative process. Gassmann's equation was then used to correct for filtrate invasion effects. Invasion effects were found to change impedance values within reservoir intervals by as much as12 %, which has implications for 4-D seismic monitoring of the reservoir.
Hydraulic fracturing is a widely used and proven technology in the industry to enhance oil and gas production, particularly in tight formations. Recent improvements in fracture fluid chemistry, proppant types, drilling strategy, and well completion technology have significantly contributed in optimizing reservoir and field development. Consequently, well evaluation and comprehensive analysis of reservoir parameters and production data is necessary to ascertain that the most appropriate stimulation treatment is selected to provide the level of productivity expected from the wells. The evaluation consists of assessing reservoir geology, open hole logs, pressure transient data, production performance, and reservoir fluid properties along with drilling and fracturing parameters. Such assessments help improve and optimize the stimulation technique for any given reservoir and field conditions, addressing specific challenges in that area, and determining remedial plans on any well that did not show expected results in terms of productivity enhancement.
Saudi Arabian gas wells are routinely stimulated to enhance and sustain production. The current strategy to drill horizontal wells and induce multiple hydraulic fractures has contributed to improved gas recovery. Due to the reservoir heterogeneity and challenges in creating optimal hydraulic fractures, some wells show high post-treatment production rate and fall into early decline.
A critical and intense work on the underperforming wells has been conducted using data mainly from geology, open hole logs, cores, fluid properties, and pressure transient tests to understand and quantify reservoir characteristics, fracture properties, and flow capacity of these wells and come up with plans to improve production. Evaluations of many wells are depicted in this paper where expected production was not achieved. The results have shown that short fracture half-lengths, limited vertical coverage, and poor fracture fluid cleanup are some of the main contributors to suboptimal post-fracture productivity. The main remedial plans to restore well productivity included the addition of perforations, re-perforations and refracturing. The refracturing treatments are designed different than the initial treatments to include some of the newer fracturing fluids, perforation strategy, and pumping schedule. This paper summarizes the well conditions, complete evaluation processes, and the remedial procedures undertaken for each well to ensure full potential. Pre- and post-remedial action program indicates the success of refracturing program.
Arukhe, J. O. (Saudi Aramco) | Ghamdi, S. (Saudi Aramco) | Dhufairi, M. (Saudi Aramco) | Duthie, L. (Saudi Aramco) | Omairen, K. (Saudi Aramco) | Ahmari, A. (Saudi Aramco) | Harbi, M. (Saudi Aramco) | Onwuliri, C. (Schlumberger) | Elsherif, T. (Schlumberger) | Othman, B. (Schlumberger)
To enhance well performance intervention work is often necessary in field developments. Challenges exist in vertical well interventions and these have been studied and improved over the years. However, horizontal well interventions pose a completely new challenge and a magnified level of difficulty. With extended reach wells certain challenges become almost insurmountable. Basic data acquisition such as production logging where profile data flow is acquired becomes almost impossible to acquire. Yet, this data is vital for decision making. While tractor aided coiled tubing has largely been demonstrated as a preferred deployment technique for cost-effective production logging and acid stimulation combined operations, most of the initial jobs where accomplished via memory production logging in these extended reach wells. This was because the Coiled tubing tractor had no inner wiring. This led to a situation where the subjects of real time evaluation of production flow profile, treatment effectiveness, and injection zone monitoring have remained an industry challenge.
A hydraulic tractor aided coiled tubing intervention was introduced as a solution for the development of the extended reach wells in a Saudi field three years ago. This solution aided in the acquisition of the previously difficult data and in addition, aided in deduction of the specific stimulation benefits such as damage skin reduction, improved drawdown, and treatment gains from injectivity increase. Some records which were also set while achieving the well's intervention objectives include 1) attaining the deepest coiled tubing (CT) reach at 29,897 feet (9.11 km) in an extended reach open hole horizontal injector well using a tractor and 2) the first application of real-time water injection profiling enabled through a wired motor head assembly via the tractor. In addition to data, other operational benefits include less equipment to the well site because the same equipment was used for both production logging and stimulation - in particular the coiled tubing reel, amongst others.
The application of real-time informed decisions was critical in overcoming challenges affecting spinner response, operating time and cost, optimizing stimulation design, and yielding a consistent injectivity increase with a true reflection of deep penetration into the damage zone will benefit operators confronting similar intervention challenges
Wang, Guang (PetroChina Daqing Oilfield Co. Ltd.) | Zhang, Dong (Daqing Oilfield Co. Ltd.) | Yin, Daiyin (Northeast Petroleum University) | Su, Yunhang (Daqing Oilfield Co. Ltd.) | Ma, Chunhua (PetroChina Daqing Oilfield Co. Ltd.)
Alkaline/Sufactant/Polymer(ASP) flooding is a new technology of enhanced oil recovery remarkably after polymer flooding. Part of the test blocks of ASP have entered into middle development phase, and achieved better effects of increasing oil and decreasing water. However, Severe heterogeneity of main oil layers leads three elements liquid fingering along the low-permeability reservoir position of every sedimentary units in thick oil reservoir. It causes the low pressure of injection wells, high polymer concentration of production wells and serious inefficient and ineffective circulation of three elements liquid. Research on profile control technology of ASP is promoted to control the increasing speed of polymer concentration of production wells, decrease the inefficient and ineffective circulation of three elements liquid and improve development effect of ASP flooding.
The current profile control agents such as typies of HPAM/Cr3+, HPAM/Al3+ and HPAM/Organic Phenolic cannot fit the alkali environment of ASP. This paper uses the method of contrast test and orthogonal design to recipe a new gel-type profile control agent which can resist the alkali environment.The content of evaluation include impact on the interfacial tension of ASP compound system, impact of the concentration of NaOH on the performance of new profile control agent and impact of slow-release formulation on gelled time. Using heterogeneous core model of flat plate of three layers, four injection and one production wells, the experiments of profile control are conducted in ASP flooding. The results show: adding 0.035 PV new profile agent in the middle of ASP flooding can improve 4.06% of recovery factor more than ASP flooding so that it has a good profile control effect.
The profile control technology for ASP presented in this paper has improved the effect of ASP to a great degree, and it is a promising tool for the successful application of ASP in Daqing oilfield.
This paper describes the design, planning, implementation details and field trial testing of a new generation integrated intelligent completion system in a trilateral well in a field in Saudi Arabia. The system consists of a flow control valve with a real time choke position sensor and annulus & tubing pressure/temperature measurements integrated as one compact piece. The integration facilitates faster deployment of the intelligent system while avoiding complexity and disruption risks that are inherent with conventional intelligent completions. Included in the description are equipment, design, installation procedures and best practices.
In the "D?? field, the wells are mostly horizontal multilateral oil producers drilled in high Darcy "A?? sand and "B?? sand reservoirs. In the trial test well; the main challenges were well placement, geo steering to "B?? sand, sand quality and thickness variance, drilling successfully through shale sections to TD, installing inflow control devices screens in the laterals, mitigating cross flow due to pressures differences, and water breakthrough deferral.
Saudi Aramco has installed numerous numbers of intelligent completions over the last 8 years. The main drivers for these completions are to balance the drawdown and rates from each lateral, prevent cross flow between laterals and choke back laterals with high water or gas inflow. The increased monitoring capabilities of the system presented in this paper will help in production optimization of the multilateral wells.
This compact integrated intelligent completion system provides: isolation, selective flow control or water shut off for each lateral, real time annulus and tubing P & T monitoring for each lateral, pressure build-up, interference testing between laterals, real time position sensor to confirm choke position, production optimization for each lateral, faster operation time due to fewer positions, enhanced reserve recovery, extended well life, reduced future intervention, and minimal production interruption.
Using variable positions flow control valve, water production can be managed to sustain longer oil production while minimizing water cut from laterals. Monitoring the flowing pressure in real time allows producing the well at optimum rate above the bubble point pressure.
Knowledge and lessons learned from this successful installation have provided an insight into this new generation integrated intelligent completion benefits and paved the road for further deployment for similar applications.
The Burgan-Wara formations from Southeast Kuwait (Greater Burgan field) constitute the largest known siliciclastic oil reservoir on earth. A specific workflow combining geological, geophysical and reservoir engineering techniques was developed to build a fully integrated and representative geomodel of the field.
The sedimentology and stratigraphy were here reviewed in terms of depositional environment and lateral stratigraphic correlation. The variability inherent to the depositional style leads to a complex reservoir scheme. Lower Burgan is dominated by stacked braided channels representing homogeneous, high quality reservoirs. Higher in the stratigraphy, lateral facies variability and heterogeneities are observed in tidal dominated units. Mud dominated units occur within the Upper Burgan and Lower Wara formations and provide good sealing capacities. Small, laterally strongly variable and heterogeneous fluvio-tidal dominated units are representative of the Upper Wara Formation.
A 3D geological model of more than 900 million cells was built, based on the new structural and stratigraphic framework interpretations to capture the complexity of the Burgan Field reservoirs. Rock-types were defined, based on more than 900 well logs and core petrophysical properties measurements. The seismic reservoir characterization, focused on inversion techniques and calibrated with the newly defined rock-types provided crucial information on sandstone proportions distribution, especially in areas with lower well control.
The first attempt to simulate, at high resolution, the largest siliciclastic oil field in the world provides a comprehensive way to understand the field heterogeneities and behavior. The updated geological model, based on new interpretations allowed characterizing the major reservoir heterogeneities and has significant impact on the reservoir management of this giant field.
Al-Salali, Yousef (Kuwait Oil Company) | Al-Bader, Haifa (Kuwait Oil Company) | Duggirala, Vidya Sagar (Kuwait Oil Company) | Manimaran, A. (Kuwait Oil Company) | Packirisamy, S. (Kuwait Oil Company) | Al-ibrahim, Abdullah (Kuwait Oil Company) | Rajkhowa, Anupam (Kuwait Oil Company)
Testing and completing deep reservoir in the state of Kuwait is challenging due to high contrast in formation pressure over the 4,000 feet section (13,500' to 17,500'). Recently, a new structure located in the North-Western part of Kuwait area was drilled and tested with deep drilling rig. Formations in this deep structure have very low porosity and permeability with naturally fractured reservoir. During short term testing, wells produced oil and gas with unexpectedly very high H2S(20%-35%), the highest H2S content in any reservoir so far discovered in the state of Kuwait. Since the reservoir was rated as HPHT and sour, it was a challenging experience to test all the wells safely and successfully. Unfavorable conditions such as high pressure, high temperature, high H2S and CO2 content require special equipment, tools and treatment to test and complete exploratory wells.
The targeted formations were perforated using deep penetration TCP guns, stimulated with emulsified/retarded acid, tested with Drill Stem Testing(DST) tools and sampling was done. Meticulous planning and testing strategies could overcome all challenges and high sour reservoir was successfully tested safely without any incident. The wells were flowed only for short period due to high sour nature of the reservoir fluid and safety reasons. However, data collected during short term testing helped in understanding production capability, fluid and reservoir characteristics which is vital for delineation/development of the new field. Methods developed, data obtained and expertise gained in testing and completing high sour wells will be useful for the future development of sour gas reservoir.
Aim of this paper is to describe the actual challenges encountered and lessons learned during testing and completion of hostile environment wells. This paper also aim to present techniques and approach adopted to address the operational risk and HSE issues during perforation, Coiled Tubing, stimulation, well testing and sampling operations.
One of the most common and cost effective secondary recovery techniques used in the industry is Electrical Submersible Pump (ESP). This technology uses the ability to pump very large volumes of fluid, by decreasing the bottom hole pressure allowing oil to flow from the reservoir and adding energy from the pump and electric motor to produce the fluid to surface.
Recent ESP designs are very effective "Intelligent?? equipment enabling real-time monitoring of well performance. Failure to ensure ESP equipment operation within the recommended operating ranges could result in a premature loss of an ESP and significant increase in operating cost.
With dynamic and changing operating environments, it is essential to continuously monitor and diagnose ESP operating conditions, leveraging real time information received from the pump, to optimize its run life and avoid premature failures.
This paper will highlight the methodology used by Saudi Aramco to adopt a state-of-the art monitoring and diagnostics solution for ESP as well as the long term strategy for advance solutions. The ultimate objective is to increase ESP run life, lower operating cost, and maximize production.
Different layers will be discussed covering Saudi Aramco' ESP surveillance and optimization approach including required infrastructure, monitoring factors, real time data requirements, basic and advanced diagnostic features associated with ESP monitoring.
Oil-base mud (OBM) is an increasingly popular drilling fluid used to protect the wellbore stability in horizontal wells drilled in China targeting shale gas or oil. In these reservoirs, an in-depth understanding of fracture attributes is critical for stimulation design and well placement optimization, but the resolution and coverage of traditional imaging technology for OBM limits the extent to which this objective may be achieved. A microresistivity imager achieving resolution and coverage similar to established technology for conductive water-base mud (WBM), fully capable to distinguish fractures and formation structural features in OBM, has been a much needed technology development to provide critical insight required for shale oil exploration.
The paper presents a case study from the Bohai Bay basin in Eastern China, where oil shale formed in the faulted depression lacustrine sub-basins of the Lower Oligocene. One horizontal exploration shale oil well was drilled with OBM for reservoir evaluation. Only a gamma ray log and new, high-definition microresistivity image logs were acquired due to difficult operating conditions, which made it a great challenge to interpret reservoir properties and optimize stimulation design. Fortunately, two nearby vertical wells were drilled and evaluated in detail prior to design of the horizontal well, making use of geochemical, advanced acoustic, and microresistivity image logs to optimize placement of the lateral, thus providing a reference for estimation of the reservoir properties.
The results showed that the new, high-definition resistivity imaging tool gives detailed images suitable for full fracture and structure characterization, and that such high-quality images are feasible even in wells drilled with OBM. Interpretation of high-definition microresistivity images to build a near-well structural model provided a framework for correlation of fracture, reservoir, and mechanical properties from the vertical wells to the horizontal well. This provided a clear picture as to how the lateral well trajectory progressed stratigraphically within the shale section, as well as the distribution of the fractures, reservoir and non-reservoir rocks, total organic carbon (TOC) and minimum geo-stress along the well trajectory. Subsequently, this rich model provided the needed critical inputs to decide how and where to complete the well with an optimized stimulation design.
AC induction motor drives are now finding increasing acceptance in various industrial applications because of the performance they can provide. Applications of AC drives vary from running simple conveyor belts and blowers to implementing a sophisticated variable speed variable frequency drives (VFD), in which torque and speed are well-regulated. Based on the type of application, choice of an appropriate control technique is made.
This paper presents a comparative study on most popular control strategies of Induction Motor Drives; constant V/Hz open/ closed loop control, field-oriented control (FOC), and Direct Torque Control (DTC).
The comparison is based on various criteria including basic control characteristics, torque performance, speed performance and transient response with respect to the load torque and speed variations.
Simulations of the above control techniques have been performed using MATLAB/SIMULINK™ software.
The Adjustable Speed Drives are generally used in industry. In most drives AC motors are applied. The standard in those drives are Induction Motors (IM). Induction motors are widely used in application such as pumps, fans, elevators, electrical vehicles, heating, ventilation and air-conditioning (HVAC), robotics, wind generation systems, etc.
Previously, DC machines were preferred for variable speed drives. However, DC motors have disadvantages of higher cost, higher rotor inertia and maintenance problem with commutators and brushes. In addition they cannot operate in dirty and explosive environments. The AC motors do not have the disadvantages of DC machines. Therefore, DC motors are progressively replaced by AC drives. The accountable for those results are the development of modern semiconductor devices, especially power insulated gate bipolar transistors (IGBT).
The most economical IM speed control methods are realized by using frequency converters. Many different strategies of frequency converters are proposed and investigated in this paper. However, a converter consisting of a diode rectifier, a dc-link and a pulse width modulated (PWM) voltage inverter is the most applied used in industry.