bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation and Analysis of Carbonate Acidization with Gelled and Emulsified Acids
Authors: Maheshwari P. , Maxey J. , Balakotaiah V.
Published: December 2014

Polymer-based gelled (or in-situ gelled) and emulsified acids have been used for matrix acidization of high-temperature carbonate reservoirs for several years. Gelled and emulsified acids are typically used to help reduce the leakoff rate from the wormhole walls as compared to non-gelled acids, resulting in deeper penetration of acid, whereas in-situ gelled acid is used for acid diversion. Literature review indicates that several laboratory scale experimental studies have been performed to analyze the effect of acid gelation and emulsion on carbonate acidization as compared to non-gelled acids. However, there are very few modeling or quantitative theoretical studies regarding carbonate acidization with gelled and emulsified acids that can be tested in laboratory or field scale. More specifically, an analysis of the transport and rheological properties (i.e., shear thinning behavior) of gelled and emulsified acids on the acidization process is not available in the literature. Therefore, the primary objective of this study is to analyze the effect of transport and rheological properties of gelled and emulsified acids on carbonate acidization in three dimension (3-D), which can help in terms of design of gelled and emulsified acids properties to achieve lower leakoff rate and deeper penetration of wormholes.

The authors present 3-D numerical simulations of carbonate acidization with HCl, gelled, and emulsified using a two-scale continuum (TSC) model. Using the model, the effect of transport and rheological properties of these non-Newtonian acids on the acidization curve and dissolution pattern is analyzed and compared to the available laboratory scale experimental data. From the numerical simulations, it has been observed that a lower amount of acid is necessary to breakthrough, and thinner wormholes are formed for both gelled and emulsified acids compared to neat hydrochloric acid (HCl). Additionally, acidization remains in the optimum dissolution regime for a large variation in terms of acid injection rate for both gelled and emulsified acids compared to neat HCl. Finally, the authors develop a wormholing criterion for acids whose rheological behavior can be described by the power-law. This criterion can be used to estimate the optimum injection rate for vuggy and nonvuggy carbonates.
Cuttings Transport Simulation Combined with Large-Scale Flow Loop Experiment and LWD Data Enables Appropriate ECD Management and Hole Cleaning Evaluation in Extended-Reach Drilling
Authors: Naganawa Shigemi , Sato Ryosuke , Ishikawa Masaki
Published: December 2014

We have performed experimental and theoretical studies on cuttings transport in directional wells for more than 15 years. During that time, we developed a one-dimensional (1D) two-layer model transient cuttings transport simulator that predicts the transient behaviors of cuttings bed height, suspended cuttings concentration, cuttings slip velocity, annular pressure, and equivalent circulating density (ECD) along the entire trajectory of the complex extended-reach well. Model parameters, such as annulus friction factor, cuttings deposition rate, and re-entrainment rate, were determined on the basis of numerous experiments we previously performed using a large-scale cuttings transport flow-loop apparatus developed to simulate complex flows in borehole annuli with various inclination angles from vertical to horizontal.

In this study, we performed model validation and cuttings transport analysis using field data in a directional well where the annulus ECD was measured by logging while drilling (LWD), and the returned cuttings rate was measured at the surface. On the basis of the simulation study, we discussed the potential of the transient cuttings transport simulator developed in the predrilling and postdrilling phase analyses and real-time analysis during drilling. Moreover, we demonstrated the interpretation of LWD data and the appropriate management of the ECD and evaluated the hole cleaning condition from the LWD data.
Fracturing in Unconventional Reservoirs can be Challenging: UAE Case Study
Authors: Alam Anwar , Mahmoud Gehad , Arif Naveed , Pooniwala Shahvir , Mendez Alfredo , Hilal Bashar
Published: December 2014

To fracture unconventional reservoirs a different approach is required to be utilized. With the day-to-day advancement in fracturing technology more unconventional formations are being routinely fractured. But now and then we come across formations which challenge modern technologies and make us think out of box.

This paper will describe the case history covering the planning and execution of one of the first "Acid-Frac" jobs in UAE. Being the first fracturing job in this formation, no previous stress gradient data was available nor were any leakoff test (LOT) or formation integrity test (FIT) results available at the planning stage. Various aspects of the reservoir and wellbore were considered, core samples of the formation were collected for testing and a 1-D mechanical earth model was developed. The paper will describe the steps taken to prepare the geological model along with the assumptions made. It will also discuss how the uncertainty of stress gradient was tackled while planning the job. Along with the unknown variables about formation, additional challenge was on the surface pressure limitation. Although tree-saver was planned to be used to protect the wellhead, the surface pressure limitation was due to wellbore completion. Based on the various unknowns and limitation on surface pressure, the job was designed. In addition to job planning, this paper will also discuss various lab tests which were conducted on the formation cores to optimally select acid fracturing fluid.

Pre-job fracturing model was run with different scenarios which helped to predict if the job could be successfully pumped within the surface pressure limitation. Operation and equipment mobilization was optimized keeping in mind the uncertainties that were predicted. The paper will go into depth covering the different scenarios which were considered while planning the job, vital role of geological model and job execution. Although job execution did not go as per plan, paper will discuss various efforts which were made to establish injectivity and how this job helped in understanding the formation better learning lessons along the way which will be implemented in future campaigns.
Five Years' Experience Using Coriolis Separators in North Sea Well Testing
Authors: Shumakov Y. , Akbayev B. , Vigo M. , Theuveny B.
Published: December 2014

Accurate, reliable, and repeatable flow rate measurements during well testing are critical for appropriate reservoir characterization. Recently, well tests have become shorter and more challenging, with the application of new interpretation techniques heightening the need for high resolution and more accurate flow rate measurements. Although conventional well test separators have seen significant improvements over the last few decades in separation efficiency, flow rate measurement accuracy, reliability and repeatability have remained immutable.

Historically, the liquid outlets of most conventional well test separators were equipped with positive-displacement or turbine-type flow meters which are not typically tolerant of debris or solids in completion or produced fluids. This results in separators being bypassed during the initial clean-up or well-flow stages, creating gaps in flow rate histories. Additionally, flow rate measurements were greatly influenced by wellsite meter factor measurements (correction coefficients), which usually did not consider fluid type or separation efficiency.

Coriolis mass flow rate meters can overcome these challenges. These meters are widely used in process facilities and highly regarded for their precision, accuracy, and simultaneous measurement of true mass flow and fluid density. However, their use in mobile and conventional well testing is still considered to be in its infancy, lacking an extensive track record and field operation experience.

This paper will summarize the benefits and lessons learnt from using new-generation Coriolis-equipped well test separators in the North Sea over the past five years. Furthermore, a series of case studies are presented, in which data provided by these flow meters was critical for successful well test operations.
Mobile Dust Collection System to Help Minimize Environmental Footprint during Fracturing Operations
Authors: Sedberry Winfred , Katke Nitinkumar , Ghatge Vishwajit , Warren Wesley , Sanda Rajesh , Bokane Atul
Published: December 2014

Fracturing treatments often require massive volumes of silica sand. This sand must be unloaded from transport vehicles into proppant storage vessels, conveyed from the storage vessel to the fracturing blender, and mixed with fluid before being pumped down hole. Silica dust becomes airborne during this process, and onsite personnel can be exposed to that silica dust.

In addition to posing a potential health risk if not handled properly or if personal protective equipment (PPE) is not worn, the silica dust can also negatively affect the fracturing equipment. It can lead to premature wear and failure of high-value capital equipment. For example, the dust increases the frequency of engine air filter changes and can plug radiator cores, reducing cooling capacity. Additionally, silica dust is highly abrasive and can cause premature wear on cylinders, bearings, gear sets, shafts, and other moving parts.

Vacuum style dust collectors for capturing airborne silica have recently been introduced on some fracturing sites. Personnel exposure to respirable crystalline silica can be reduced and the negative effects on equipment minimized when using these dust collectors. However, one challenge introduced by the use of the collector is the need for packaging and disposal of the captured dust. This paper discusses an apparatus and ergonomic method for packaging and disposing of the dust once it is removed from the air. The apparatus is composed of a plenum chamber formed in a funnel or a frustum configuration that discharges into a distribution assembly. The distribution assembly includes a number of individual chutes, each equipped with a circular collar at the outlet, facilitating the attachment of dust collection sacks. The plenum chamber, distribution chute assembly, and individual dust collection sacks are supported by a frame assembly. This apparatus is used to package the material exiting the dust collector in easily transportable containers.
Use of Micro-encapsulated Phase Change Materials to Regulate the Temperature of Oilwell Cement
Authors: Pang Xueyu , Goel Vivek , Jimenez Walmy Cuello
Published: December 2014

During oilwell cementing operations, many situations occur for which it is crucial to regulate the temperature of the cement slurry during and after its placement. Limiting the temperature increase of cement-based composite materials has been traditionally achieved by reducing the heat of hydration of the composite (e.g., through the use of supplementary cementitious materials or inert filling materials). However, the total amount of heat generated by a cement composite is primarily determined by the hydration extent of the cement, which has a strong correlation with the composite's strength development. Reducing the heat of hydration of oilwell cement through chemical means typically results in lower strength of the material, especially during early ages.

This study investigates the application of a novel material, namely microencapsulated phase change materials (MPCMs), to regulate the temperature of oilwell cement using a physical method. The MPCM acts as an energy storage medium that absorbs heat when the temperature of the cement reaches the melting point of the PCM and releases heat when the temperature drops below its freezing/crystallization point. The solid polymer shell that encapsulates the PCM prevents the melted material from chemically interacting with the cement matrix. Hence, the strength development of the cement matrix is largely unaffected. Moreover, the set cement composite appears to be more elastic and less brittle because of the addition of the MPCM, which is beneficial to the long-term integrity of the cement.

During this study, the heat evolution of cement slurries was investigated by both isothermal calorimetry and semiadiabatic tests. A similar amount of heat was generated by most slurries, as shown by isothermal calorimetry tests. However, results from semiadiabatic tests and compressive strength tests show that the slurry prepared with MPCM in a solid state exhibited minimal temperature increase and optimal mechanical properties (high-strength and high-strain capacity), which can be attributed to desirable properties of the PCM, including high latent heat, high specific heat capacity, as well as high elasticity.
Planning and Implementing a SCAL Sample Selection Strategy for a Giant Carbonate Field Offshore Abu Dhabi, U.A.E.
Authors: Shebl Hesham , Tamimi Mohamed Al , Boyd Douglas , Muhairi Bashayer Al , Neyadi Abdulla Al , Jawhari Mohamed Al
Published: December 2014

Despite the importance of Special Core Analyses (SCAL) data to the construction of accurate reservoir simulation models, there is a lack of specific industrial guidelines for acquiring core and selecting representative plug samples, particularly for heterogeneous carbonate reservoirs. The aim of this paper is to share the strategy, practices and techniques Zakum Development Company (ZADCO) applied to obtain representative SCAL samples. There are two main aspects to the strategy; (1) coring and (2) plugging. The first stage is determining the parts of the reservoir to target for core acquisition. This requires an understanding of the distribution of static reservoir rock types (SRRT) in the reservoir and their importance to reservoir flow dynamics and fluid storage capacity. The second stage is designing a plugging program to identify reservoir rock types while maintaining the wettability of the samples intended for tests. For the second part, two adjacent sister plugs are acquired, one is a 1 inch diameter plug and the other is 1.5 inch diameter. The 1 inch diameter plug is used for static reservoir rock type (SRRT) identification using porosity, permeability, thin sections and high pressure mercury injection. The 1.5 inch diameter sister plug is preserved to maintain wettability and later used for SCAL measurements. Prior to selecting plug locations, a continuous, 0.5 mm resolution, 3D Computer Tomography scan of the 4 inch diameter whole core is examined. The scan has a high enough resolution that algal and rudist batches are visible. Accordingly, specific rock types are identified visually and targeted. After completion of SCAL measurements, the SCAL plug SRRT is confirmed, utilizing porosity / permeability measurements, thin section description and high pressure mercury injection. The majority of SCAL SRRTs matched the sister plug SRRTs, providing confidence in the technique.
Subsea Pipelines Integrity Management – ZADCO Approach
Authors: Trojette Mohamed Zouheir , Al Hammadi Mohamed , Al Alawi Faisal
Published: December 2014

Zakum Development Company, a major Oil and Gas company in the UAE, operates three offshore oil fields which are located at 65, 20 and 80 kms northwest of Abu Dhabi and are in shallow water with depth ranging from 6 m to 30 m.

ZADCO operates a large portfolio of subsea pipelines. Most of these pipelines have been in service for more than 30 years and corrosion is a major threat to the integrity of these lines. More over the increase in water cut, the decrease in the flow rate for some lines and crude composition changes mainly increase in H2S and CO2 levels are added challenges.

To mitigate these challenges, ZADCO has in place a series of barriers which include corrosion controls like chemical injection (corrosion inhibitors, biocides), maintenance pigging, etc.

Also ZADCO implements several corrosion monitoring activities like corrosion rate monitoring, intelligent pigging of the pipelines, verification of the In line Inspection results using Automated Ultrasonic inspection (Auto-UT) as well as fitness for service and remnant life assessment prior to repair and rehabilitation.

This paper presents ZADCO approach to manage the integrity of its subsea lines network and covers: –ZADCO Asset integrity management policy–Asset integrity Management System (AIMS)–Pipeline Integrity Management System Requirement (PIMS)–Intelligent Pigging–Corrosion Mapping (Auto Ultrasonic Verification)–Fitness for Service and Remnant life Assessment–Repair and rehabilitation plans–Concluding remarks
First-Ever Level 4 Multilateral Well in North Kuwait Successfully Completed, Improves Oil Production
Authors: Al-Khaldy Meshal , Dutta Abhijit , Goswami Bijan , Al-Rashidi Ali , Rondon Leonque , Warraky Mohamed , Samie Mohamed
Published: December 2014

Kuwait Oil Company (KOC) has recently drilled the first multilateral well in a North Kuwait field to improve oil production in productive layers subjected to water coning problems by increasing reservoir exposure using Level 4 multilateral technology. The multilateral well targeted the same sand in different directions with two laterals. Both of the laterals were drilled using rotary steerable drilling systems to reduce drilling time. The drilling process used a full suite of logging while drilling (LWD) tools, including azimuthal deep resistivity technologies, to ensure the well path is precisely geosteered within the reservoir boundaries and density/porosity tools in real-time, combined with specialized modeling software to position the well in the best possible reservoir.

Level 4 multilateral technology was selected after performing an extensive geological assessment and studying the challenges of exploiting oil in the target sand reservoir. The 12 1/4-in. main section was cased and cemented with 9 5/8-in. casing to the landing point; the 8 1/2-in. lateral-I was drilled and completed with 5 1/2-in. inflow control devices (ICDs). The sidetrack was performed by cutting a window from a specialized latch coupling in the 9 5/8-in. casing; the 8 1/2-in. section was drilled to the landing point, and the 7-in. liner was run and fully cemented. The 6 1/8-in. lateral-II was drilled and completed with 4 1/2-in. ICDs.

The fully cemented and cased junction or bifurcation should help achieve greater well integrity and prevent fluid migration from the adjacent area, while the specialized latch coupling should help ensure easy access to either of the laterals, as required. The ICD technology and swellable packers were selected to delay water breakthrough from an active aquifer.

This publication describes the application of multilateral and geosteering technologies, and analyzes the advantages and disadvantages of the first multilateral well drilled in North Kuwait that began with a campaign of higher order (Level 4) multilateral. The well is considered to be a pilot well to identify the feasibility of using multilateral technology as a production model to help enhance oil recovery and reduce drilling costs in the field by replacing the cost of drilling new wells.
Advanced Completion and Stimulation Design Model for Maximum Reservoir Contact Wells
Authors: Sau Rajes , Shuchart Chris , Grubert Marcel
Published: December 2014

This paper introduces a novel computational simulator for advanced completion and stimulation design of Maximum Reservoir Contact (MRC) wells. Using innovative computational algorithms, this simulator models numerous challenging physics of acid stimulation and transient injection of multiple fluids through openhole complex completions, e.g. Limited-Entry Liners (LEL) and Inflow Control Devices (ICD) in MRC wells. LEL hole or ICD nozzle diameter, hole distributions, and packers are explicitly modeled as part of the completion. The fast, robust simulator tracks concentrations and models flow of multiple fluids while explicitly accounting for completion and formation pressure drops along the lateral and transient reservoir dynamics. Fluid invasion and stimulation distribution (wormhole and skin) along the lateral are computed by the simulator which is coupled with a dynamic wormhole model.

A case history of the model application is presented. The model was used to design a limited-entry liner with 4 mm holes distributed non-uniformly among 12 compartments. The liner enabled successful high-rate bullhead stimulation of an 11,500-ft lateral, resulting in reduced cost, limited risk, and elimination of the need for coiled tubing. Model validation and calibration against the field data is discussed. Detailed evaluation of the well data suggests successful stimulation of the entire lateral and production uplift from every compartment.

The paper presents a novel, fast simulator to model transient fluid placement through complex completions in MRC wells. The capability to robustly model a complex completion in long openhole laterals has enabled the design of successful bullhead acid stimulation through a limited entry liner. Apart from acid stimulation design, the simulator also provides capabilities to model various well injection processes in sandstone and carbonate reservoir, such as scale squeezes, solvent treatments, and HF acid treatments.
Embracing Elevated Safety Tenets through Engineering Design
Authors: Katke Nitinkumar , Ghatge Vishwajit , Bokane Atul
Published: December 2014

This paper proposes adoption of a revised mindset with respect to safety by collaboratively implementing design and development. Given the nature of possible risks involved during operations, safety is a priority within the oil and gas industry. Transformation to an ideology of safety through engineering design requires a series of stages involving designing for safety at the nascent stage, prototyping with deliberately provided safety features, evolving the mindset by overcoming the resistance for change, and boosting the safety attitude, thus developed through continual practice.

A case study is presented in which field personnel were involved in the collaborative design process to seek input regarding the safety platform for trailers. To avoid trip hazards, landing steps, handrails, lock pins, and safety doors were designed to The Occupational Safety and Health Administration (OSHA) guidelines. Working at heights and ladder accessibility from a safety perspective is also addressed. Roller bearings have been devised to align the movement of platform in linear direction and to move the platform in open/work position. The position of the platform is locked by providing a locking nut. In a second case study related to offshore skids, numerous minor design changes were incorporated and computer simulated to help ensure the selection of a safe design. Fiber gratings were used on top so that slings would not fall down on equipment and the personnel working within the vicinity. Thirdly, a design process was developed wherein design teams provided input of various options for avoiding pinched fingers. This approach for an all-inclusive and collective discussion has helped to further evolve the outlook toward safety as a core value.

Infusing safety as a key element of the thought process creates immense value across industries in terms of applicability. A proper safety attitude can lead to significant returns in terms of reduced risk, workforce protection, enhanced quality, and improved overall economics. Addressing health, safety, and environment (HSE) risks, the safety platform and skids discussed here are now deployed in the field. The response from the end users is encouraging. Embracing safety focused thinking during engineering design helps provide an impetus toward bolstering safety culture.
Simulation of Residual oil Saturation in Near-miscible gas Flooding Through Saturation-dependent Tuning of the Equilibrium Constants
Authors: Patacchini Leonardo , Duchenne Sébastien , Bourgeois Marcel , Moncorgé Arthur , Pallotta Quentin
Published: December 2014

Conventional miscible or near-miscible gas flooding simulation often overestimates oil recovery, mostly because it does not capture a series of physical effects tending to limit interphase compositional exchanges. Those can be for instance microscopic bypassing of oil situated in dead-end pores or blocked by water films, as well as macroscopic bypassing due to sub-grid size heterogeneities or fingering.

We here present a new engineering solution to this problem in the near-miscible case, relying on our in-house research reservoir simulator (IHRRS). The principle is, while using a black-oil or an equation of state description, to dynamically decrease the K-value of heavy components and possibly increase the K-value of light components as the oil saturation reaches the desired residual limit; this enables changing the phase boundaries when needed while preserving the original fluid behavior during the initial production stages.

The benefits of the proposed method are demonstrated on a reservoir conditions tertiary gas injection experiment, performed in our laboratories, for which residual saturations as well as oil phase and individual components production rate have easily and successfully been history matched. Results are then compared to matches obtained using saturation exclusion and α-factors methods. As a proof of concept, suitability of the method to simulate incomplete revaporization of condensate during gas cycling is also illustrated, on the third SPE comparative solution project case.
The Longest Horizontal Well Drilled in The U.A.E., Geosteered in a Thin Calcareous Dolomite Sublayer
Authors: Abbas Nashat , Al Nokhatha Jamal , Farouz Ameer , Mohamed Emad , Abbas Syed Haidar , Hui Wang
Published: December 2014

September 2012, ZADCO drilled the longest well to date in the U.A.E. to test the productivity and injectivity of a low permeability, carbonate reservoir in a giant Middle East oil field. The extended reach well was drilled to a total measured depth of 24,390 ft., with a horizontal length of 11,015 ft.

The borehole target zone was a ~3.5 ft. thick calcareous dolomite sublayer sandwiched between upper and lower ~4 ft. thick limestones. The critical factors for success were: (1) LWD tools capable of differentiating calcareous dolomite from the nearby limestones; and (2) LWD sensors close to the bit as possible to enable prompt geosteering reactions to possible lateral facies changes. Challenges were: (1) the capability of the jackup rig to drill the required distance; (2) minimizing hole undulations; and (3) remain within the 3.5 ft. target zone. Concerns were raised about the use of nuclear chemical source density tools and the risk of a lost nuclear source in hole should the drill pipe become stuck. To address these concerns, the second half of the lateral section was steered without a chemical nuclear source in the downhole tool string.

A LWD formation pressure test tool was run post drilling to evaluate formation mobility. The result supported well placement in the higher permeability dolomite layer which was later validated by production and injection results.

This paper illustrates good geosteering practices in a challenging long horizontal well with carefully selected LWD program to achieve the target and reduce risks.
Wellbore Stability Analysis Using Acoustic Radial Profiles and an Elastoplastic Model
Authors: Hamid Osman , Rahim Zillur , Ba-wazir Omar A.
Published: December 2014

Wellbore instability during drilling, completion, and production is important and costly issue in many oil and gas fields. Field observations show that stress-related wellbore instability challenges are frequently encountered. Estimating stresses and mechanical properties is a key to the success of drilling, completion and production operations. Knowledge of accurate Unconfined Compressive Strength (UCS) is essential for understanding wellbore stability, perforation efficiency, and sanding tendency. UCS along the wellbore and perforation is a key input of failure criteria and can be best obtained from laboratory core testing that are mostly performed in the reservoir section. Cores from the overburden formation are rarely taken, although most wellbore stability related issues are encountered in this section of the well.

In this study, wellbore stability modeling was conducted using Finite Element Modeling (FEM) to predict induced stresses and yielded zone around the wellbore in the elastoplastic media. Elastoplastic models were used in conjunction with the Mohr-Coulomb and modified Lade yield criteria.

UCS is calculated by matching the resultant stresses around wellbore with dipole radial profiles from the Acoustic Scanning platform. The damage or yielded zone is interpreted by means of volumetric strain analysis. This damage provides an indication of the potential breakout that might occur during drilling, thereby giving an indication of the risks to wellbore instability.

This novel technique is applied to compute wellbore stability in the Khuff and pre-Khuff Formations in Saudi Arabia. The methodology can be applied to other locations using similar approach that combines acoustic radial response and FEM.
GASCO's Initiative for Emission Reduction in Oil & Gas Plants – Gas Turbine Replacement Project
Authors: Al Hammadi Nasser
Published: December 2014

The reduction of greenhouse gas emissions from oil and gas plants is without a doubt gaining widespread interest from leading companies around the world. Implementation of effective and best practice technologies to minimize greenhouse gas emission levels by the oil and gas industry will substantially lead to a better emission reduction practices and eventually increase the public confidence in this sector.

Many of the existing plants – especially those which were built 20 to 30 years ago – and are still in operation invariably have Gas Turbines mostly for power generation and process gas compression application. The exhaust from these turbines contributes substantially to increase emission levels.

Systematic approach is required to explore cost effective and practical alternatives to replace these Turbines with state of art non-emitting drives to reduce greenhouse gases which are emitted at present.

This paper presents GASCO's stepwise approach to determine most energy efficient & cost effective alternatives to replace emitting turbines as well as achieve a long-term reliable performance

This paper also presents a detailed implementation strategy from conceptualization to commissioning of new units and phasing out of old Turbines. It also describes critical reviews and decision making required at intermediate steps.

This paper, which details initiatives taken by GASCO to reduce emissions from the turbines and bringing additional advantages in form of improved reliability and increased longevity of the operating plants, will certainly provide insight to operators of similar plants to initiate measures for emission reduction and thus contribute substantially to protection of environment
Performance Review and Field Measurements of an EOR-WAG Project in Tight Oil Carbonate Reservoir – Abu Dhabi Onshore Field Experience
Authors: Figuera Luis , Al-Hammadi Khaled , Bin-Amro Khaled , Al-Aryani Fatema
Published: December 2014

A Water-Alternating-Gas (WAG) scheme is a proven enhanced oil recovery (EOR) method. The first WAG project was reported in 1957 and until today more than sixty (60) field experiences can be found in the literature. Most of the published experiences report 5-10% additional oil recovery over waterflood. WAG injection can lead to improved oil recovery by combining better mobility control, improved microscopic displacement, and better sweep efficiency.

This study presents a recent field experience where a miscible WAG injection has been designed and implemented with the objective of enhancing oil recovery in a heterogeneous, low dipping, and tight carbonate reservoir. The project has been performed on close-spaced slanted wells and utilizes rich hydrocarbon gas. Since the beginning of the injection, an integrated surveillance program has been applied to determine whether the miscible flood is working efficiently. This program involves observation wells, time-lapse saturation logging, well testing, tracer injection, and i-field technology along with numerical simulation.

This paper presents a review of the main findings, issues and lessons learned during eight (8) years of EOR-WAG injection. The paper discusses the project design, the integrated surveillance program and the WAG mechanisms to enhance oil recovery. It also summarizes worldwide WAG experiences based on published field observations.
Pushing the Limits of Distributed Temperature Survey Analysis in Mega-Reach Power Water Injectors
Authors: Dhufairi Mubarak , Yateem Karam , Duthie Laurie , Kilany Khaled , Elsherif Tamer , Ahmed Ramy
Published: December 2014

Increases in well complexity and stimulation challenges have led to more complicated stimulations. The challenge that consistently arises after conceptually designing the treatment is how to determine the zonal coverage and evaluate the stimulation, especially in extended reach wells in carbonate reservoirs. Significant effort has been spent on using modern technologies to qualitatively evaluate zonal coverage and estimate the skin factor evolvement after the treatment. No work has yet answered the following question: How does matrix acidizing alter near-wellbore permeability and affect the zonation of the wellbore when treating carbonate reservoirs?

In long horizontal wells that are drilled in carbonate formations, it is believed that wormholing significantly alters the near-wellbore apparent permeability. Nevertheless, methods to estimate the change in permeability resulting from a matrix treatment are not known, and usually the change is accounted for in simulators by assigning a very low skin value. Other work conducted in carbonate reservoirs using pressure transient analysis (PTA) techniques has shown that applying a change in permeability is necessary to obtain a type-curve match.

This paper presents an innovative workflow and algorithm to estimate the changes in the critical matrix rock properties and how to incorporate these changes into further simulation. The algorithm integrates the while drilling mobility data, open hole porosity logs, pressure transient data, distributed temperature survey data, and production logging data to verify the accuracy of the model by using the flow rate as the control parameter for iterations.

A case study shows how we could derive a flow profile for the pre-stimulation stage, optimize matrix stimulation treatments in real time according to the formation response and diversion efficiency, define reservoir zones that are contributing to flow before and after the treatment, and finally, estimate new values of permeability and skin to be utilized in post-treatment reservoir simulations.
Production Engineering Specialist Program is Helping Saudi Aramco to Meet Technical Challenges in Upcoming Mega-Projects
Authors: Yateem Karam S. , Warsi Syed , Alsyed Samih M.
Published: December 2014

In a quest to maintain and enrich its employees’ knowledge base to not only have competitive edge but also prepare the workforce to handle the ever increasing complexity in hydrocarbon extraction and production, today's energy companies employ training programs to equip their experienced personnel with skills that can be utilized to effectively handle challenging projects. Saudi Aramco, among many technical specialist programs, has also developed an all-encompassing training program for experienced professionals, which upon completion will allow the individual to perform duties as a subject matter expert (SME) in production engineering related job skills. This accelerated Production Engineering Specialist Program (PESP) is designed to make the transition from a young professional to an expert in a specific subject with a customized approach to his background and tailored to his future career path.

PESP is applicable to young engineers after attaining five years of post-university experience, exposing them to various facets of production engineering and focusing on an explicit specialty. The Program incorporates seven specialties, all related to Production Engineering. These specialties are Stimulation, Well Completion, Electrical Submersible Pumps, Well Intervention, Well Treatments, Production Optimization and Intelligent Field. Completion of the Program is time-based but rather mandated by completing predetermined tasks in all aspects of the respective specialty and customized to the participant's background.

The program has yielded several graduates since its inception. It is a proven successful program, which has allowed PESP graduates to move around the company in assignments, targeted to provide support expertise in their related specialty in challenging situations. The paper will provide details of the PESP structure, typical Individual Development Plans (IDPs) for these seven specialties and how PESP graduates can help the company to meet the technical challenges for upcoming mega-projects by utilizing their expert knowledge as SMEs. PESP has a broader scope to build an interchangeable pool of SMEs that can minimize the need and dependence of acquiring knowledge from service companies and in addition be able to train future generations of young professionals.
Water and Gas Control in Naturally Fractured Carbonate Reservoirs: Development of a Novel Polymer Gel System with Foaming Properties
Authors: Vasquez Julio , Lewis Chris , Eoff Larry
Published: December 2014

Excessive undesired fluid production of water or gas can limit the economic life and profitability of hydrocarbon reservoirs. A variety of techniques for controlling water production have been attempted within the oil industry, including mechanical and chemical treatments. Chemical treatments can become more challenging when applied in reservoirs with either natural or induced fractures. More specifically, placement control becomes a critical factor, particularly within highly fractured and depleted reservoirs. This paper presents the development and optimization to further improve a widely used organically crosslinked polymer gel system by adding foaming properties to the innovative fluid system. Referred to as a foamed conformance polymer (FCP) in this work, the system can improve placement in naturally fractured carbonate formations for water and gas control applications.

The standard (nonfoamed) organically crosslinked polymer system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). This FCP system can be foamed up to 70% v/v quality to be applied within a wide temperature range (40 to 350°F) with little to no effect on gelation time, providing a stable foam that maintains sealing properties. This paper discusses the following parameters: (1) FCP advantages and considerations, (2) FCP system components to develop foam properties, (3) FCP performance testing to optimize foaming properties up to 70% v/v quality at elevated temperature, and (4) sealing capabilities of the FCP system. Addition of foaming properties to this conformance polymer gel system adds the following benefits: (1) improved placement in depleted, naturally fractured or fissured carbonate reservoirs, (2) reduced hydrostatic pressure (density can be lowered to ~2.4 lbm/gal), allowing better control of surface pressure while placing the treatment into the targeted zone, (3) improved ability to fill fractures and displace reservoir fluids by providing a system with fluid-loss control properties, and/or (4) diverting fluid properties for optimum coverage when targeting long intervals. The FCP produces a high-quality, stable foamed solution to help effectively seal natural fissures and fractures for reduced flow of unwanted water and/or gas.
Subsidence Evolution of the Musandam Peninsula & Subsurface Architecture of the Pabdeh Foreland Basin
Authors: Aidarbayev Sanat , Ali Mohammed Y.
Published: December 2014

Surface and subsurface geology of the Musandam Peninsula recorded a tectonostratigraphic evolution of the northeastern Arabian Plate since the late Permian. In order to quantitatively determine this evolution, backstripping method has been applied to two exploration wells located within and around the Musandam Peninsula. The backstripping technique uses stratigraphic data extracted from the wells and quantitatively determines the depth that basement would be in the absence of water and sediment loading. As a result, the tectonically-driven subsidence data allows us to determine basins developed within the study area and their driving-mechanisms to form.

The tectonically-driven subsidence data from the wells recorded development of a rifting and two flexural foreland basins. The rifting episode formed in response to a continental breakup and opening of Neo-Tethys Ocean, approximately from ~ 185 to ~ 93 Ma. Heating and stretching of the continental lithosphere at the time of the rifting caused the lithosphere to subside. After this rifting event, the tectonic subsidence curves indicate that the studied area was subjected to evolution of two foreland basins after two uplift events happened around ~ 93 and ~ 25 Ma. We refer these uplifts to the Late Cretaceous Semail Ophiolite obduction and the late Tertiary Musandam culmination, whereby both of them produced lithospheric loads on the top of the northeastern Arabian plate and led to a development of two foreland basins, Aruma (~ 80 to 25 Ma) and Pabdeh (~ 20 to present day), respectively.

With the rise of interest for unconventional resources, we have to better evaluate the essential petroleum system elements. Normally, the total subsidence (tectonically-driven plus sediment and water loading) is used to construct the burial history of a basin. Since the backstripping method is able to separate the tectonically-driven subsidence from the total subsidence, we can exactly pinpoint the deposition time of deep-water sediments which can act as a source rock or an impermeable seal. In addition, the tectonic subsidence curve was able to identify precise ages of two uplifts which mark the critical timing of potential structural traps and migration pathways for hydrocarbons.
EOR Options for Heterogeneous Carbonate Reservoirs Currently Under Waterflooding
Authors: Masalmeh Shehadeh K. , Wei Lingli , Blom Carl , Jing X. D.
Published: December 2014

Carbonate reservoirs in the Middle East are highly heterogeneous with complex porosity systems and mixed-wet matrix properties. These characteristics strongly affect reservoir performance under waterflooding. This paper concerns a highly layered limestone reservoir with various levels of cyclicity in properties and can be described at a high level as consisting of two main bodies, i.e., an Upper zone and a Lower zone with permeability contrast of up to two orders of magnitude. The main part of the reservoir is currently under waterflooding. Field observations show that injected water tends to channel quickly through the Upper zone along the high permeability layers and bypass the oil in the Lower zone. Past studies have indicated that this water override phenomenon is caused by a combination of high permeability contrast and capillary forces which counteract gravity forces.

In this paper we will investigate different development options for such heterogeneous mixed-wet reservoirs aiming at improving recovery from the Lower zone: 1- Optimized waterflooding with infill wells, 2- Novel EOR options designed to overcome the capillary forces and improve vertical sweep. The EOR options include (a) polymer-assisted solutions consisting of injecting polymer in the Upper zone and water or miscible gas in the Lower zone; and (b) surfactant assisted solutions (foam and enhanced gravity drainage).

The main conclusions of the study are: 1- Waterflooding is an efficient recovery mechanism for the Upper zone and tight well spacing is required to improve recovery from the Lower zone; 2- The EOR processes have the potential of improving recovery from the Lower zone; 3- The most attractive EOR schemes are the polymer-based options which, when compared to the optimized waterflooding/infill scenario, lead to much higher recovery, lower volumes of water injected and significantly less water cycling and the requirement of fewer wells. The polymer-assisted solutions also require injecting much lower polymer volumes compared to conventional polymer flooding. Simulation results show that the process(es) are robust to injection rates, vertical heterogeneity, well completions and a range of polymer viscosities.
Non-Deterministic Approach to Define a Robust Development Plan: a Complex Mature Carbonate Field Case Study
Authors: Barroso Viseras F. J. , Blanchais S. , Verdiere S. , Bouzarkouna Z. , Schaeffner A. , Jannes P.
Published: December 2014

As oil production demand increases, the industry as a whole faces the need to constantly renew its reserves by either discovering new fields or giving a second life to mature fields. The latter is particularly challenging for geoscientists and reservoir engineers. This paper presents a non-deterministic approach used to design a robust development plan for a complex mature carbonate field with more than a hundred wells and forty years of production history.

This innovative approach can be applied to any redevelopment project for uncertainty assessment and risk management.

The first step is a 2G&R synthesis performed by a multidisciplinary team to gather all the data, verify their consistency and assess the key heterogeneities and potential influential parameters to quantify the different production mechanisms. At this crucial stage, experimental design is extensively used. This synthesis enables a solid history-matched simulation case with an associated redevelopment strategy to be built efficiently. Secondly, the thorough knowledge of the field and the expected production mechanisms in the redevelopment phase are the key drivers to identify the most impacting static and dynamic parameters. These parameters are used as inputs for experimental design on both historical and redevelopment periods. Assisted History Matching techniques enable multiple simulation models honoring historical data to be found; the quality of these models is assessed by considering different objective functions. The history-matched models are then used to derive a reserves distribution for the project. Models outputs are combined to generate 3-D probability grids for properties such as oil saturation, in order to optimize the initial development plan and improve its robustness.

This study highlights the importance of a strong and consistent 2G&R synthesis. An in-depth understanding of the field, combined with Assisted History Matching techniques, leads to models that honor the long production history, enabling the development scenario to be optimized.
Production Optimization over 20% with Artificial Lift ESP Pilot Systems in Mature Oil Field, Case Study from Middle East
Authors: Aguilar Hector , Al Marzooqi Aref Ali , El Sonbaty Tarek Mohamed , Villarreal Leigber
Published: December 2014

This paper reviews the production optimization strategy of an artificial lift system that has been implemented in a carbonate reservoir in an Abu Dhabi onshore field. The adapted optimization technique assures the mitigation of the main challenges related to reservoir heterogeneities, in addition to completion design which has a significant impact on ESPs sizing, operation and optimization processes.

An integration approach of reservoir dynamic data and ESP performance was established as a guideline for ESP surveillance, diagnostic and targeting candidate for production optimization by implementing at least one of the possible solutions: (a) upgrading ESP-surface equipment, (b) anticipate WO for re-sizing & ESP Deeping jobs, (c) well design strategy review.

The result of this effort demonstrates the successful implementing of proposed solutions by enhancing the oil production by more than 20% in all separates pilot tests conducted in the field. The project success can lead the way forward for future ESP application in similar harsh down hole conditions.