bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic Interpretation Based on Mechanical Deformation Process
Authors: Pussacq Alice , Fu Qiang , Malvesin Emmanuel , Panhaleux Solene
Published: March 2015

It is a common workflow in commercial software packages to identify stratal features through flattening techniques. However, classic and proportional flattening methods have inherent drawbacks because they do not allow for use of physical laws and rock properties. The use of common mechanical-based restoration methods is also limited because of their low performance. In this paper, we propose use of a mechanical deformation technique based on the finite element method (FEM) to balance seismic data to a hypothetical domain. The conversion makes the interpretation process more reliable for quality control (QC) of structural analysis in an interpretation-friendly environment.

Introduction

One basic step of the seismic interpretation is picking horizons, which can be auto-tracked or performed manually. The fundamental principle behind this operation is the seismic events that are relict depositional surfaces or bedding planes formed nearly instantly in terms of geologic time and that follow geologic boundaries (Catuneanu, 2010; Zeng, 1998). As results of the tectonic deformation and the effect of deposition (for example, sigmoid shape for shore-face depositional pattern), horizons are no longer flat. To remove the effect of the structural deformation (folding and faulting) in the geologic time space, several techniques have been proposed and various software packages have been developed to un-fault and flatten the depositional sequences (Stark, 2004; Stark 2005; De Bruin, 2006).

A classic flattening method can be performed by applying a simple vertical shift, based on one particular continuous horizon, for every trace in 2D seismic sections or 3D cubes (Fu, 2010). Its use is very limited. The proportional layering technique, an improved classic flattening approach, was proposed in the mid-1990s to create approximately paleo-depositional data. It is based on the assumption that the thickness between layers (time or depth domains) follows a linear relationship. Both methods are purely geometrical and very convenient because of their computing efficiency. Their biggest issue is that there is no consideration for tectonic events and geologic depositional trends. They are just converting to an artificial domain to make the interpretation easier. This process can smear the chronostratigraphic information inside the fault zones or even in the whole section (Figure 1). Essentially they are a 1D shifting technique and no attention is paid to the fundamental principles used to govern rock deformation.
The First Subsea Completion by an Operator in KN Field, Offshore Malaysia
Authors: Mahadi K. , M. Nizam M. Izzat , Ogbonna C. , Jadid M.B.
Published: March 2015

The KN field in KM cluster is located approximately 200km offshore, at water depths ranging from 59–102m. The field is part of the KM Cluster Integrated Development Plan, where the primary objective for KN field development is to recover the reserve from fringing pinnacle reef carbonate reservoir, expected to be achieved through two deviated 7-inch open-hole monobore subsea wells. KN field is expected to deliver around 200 to 300 MMSCF/day to the LNG plant to help relieve an anticipated gas shortage, as such failure to deliver the target would definitely upset the gas supply.

Besides cost savings, the shallow water subsea development concept is part of the company's long-term vision to train its staff with new technologies and prepare them with basic guidelines for future development especially in deepwater. Although this is already considered a norm in other parts of the world, subsea completion is relatively a new experience in the company operation.

The open-hole sections were drilled using Potassium/Sodium formate fluids with calcium carbonate as weighting and bridging agent and later the wells were completed with Cessium formate. Based on extensive laboratory test, it was found that this formate fluids allow for thin mud filter cake that can be remove effectively with differential pressure alone, excluding the need for filter cake breaker. High rate acidizing was planned as contingency should the wells failed to deliver the targeted well deliverabilities. Based on transient simulation using OLGA, high rate clean-up were planned to ensure effective filter cake break-up, removing debris and confirming the technical potential of the wells. With high rate, the duration of well clean-up is shorter and effective thus saving rig time.

This paper details the planning and execution towards achieving the successful project of KN field, the 1st subsea development in the company
Natural Gas Vehicles Will Develop Greatly in China
Authors: Wang Zugang , Lv Jianzhong , Rao Libo , Yang Yan , Gao Hui
Published: March 2015

Increasingly abundant natural gas is under consideration as a replacement for fuel in transportation because of the high oil prices. The number of natural gas vehicles (NGV) in China is over 1 million. The use of compressed natural gas (CNG) is growing in short-haul urban fleets, and the liquefied natural gas (LNG) is the best alternative for long distance passenger and cargo vehicles which represent most of truck diesel demand. In this paper, we analyze the driving force of NGV to make inroads and the challenges of development, and draw a conclusion that NGV with the supporting industry in China will develop rapidly in the coming years.

The great development of China automotive industry leads to the tremendous increase of vehicles in recent years. The automobile emission coming from the increasing consumption of gasoline and diesel has become an important source of air pollution and climate change. Natural gas (NG), a kind of clean energy, which can greatly reduce air pollution and promote the low carbon economy, has drawn more and more attention all over the world. Natural gas vehicle (NGV) with great prospect grows rapidly in China because of the advantages of cleanliness, efficiency, economy and security.
Real-Time Modeling-While-Drilling for Optimized Geosteering and Enhanced Horizontal Well Placement in Thin and Complex Reservoirs
Authors: Saikia Kalyan
Published: March 2015

With the growing demand for hydrocarbons, enhanced horizontal well placement resulting from optimized geosteering is becoming increasingly important. Optimal geosteering is accomplished by selecting the proper combination of logging-while-drilling (LWD) and measurement-while-drilling (MWD) tools as data acquired from these tools are directly deployed for interpreting and monitoring the well. In fact, achieving maximum success in geosteering is only possible through real-time interpretation and modeling of MWD/LWD data while drilling. Additionally, real-time 3D model updates while drilling deliver maximum guidance and assistance in geosteering to the proper well position by predicting the geology ahead of the bit. As a result, well placement risk is reduced because the associated uncertainty is quantified.

A meaningful modeling-while-drilling campaign is greatly dependent on three main factors:uninterrupted real-time data transmissionuse of appropriate software modelingselecting adequate modeling techniques

Log modeling and 3D geocellular property modeling-while-drilling are two widely used variants of modeling-while-drilling. Log modeling generates a series of modeled log responses along the planned well path considering the offset well information. Whereas 3D geocellular property modeling-while-drilling is comprised of two steps i.e., fine layering and gridding (FLG) followed by property simulation and regular model updates with new real-time log and well pick information. Each of these techniques requires MWD/LWD data, well picks, and surface grid information as input and uses different algorithms to complete the modeling. But, to obtain effective results both the simplicity and the adequacy of the modeling technique play a very important role in the procedure.

In this paper, examples from two complex and challenging wells are described in terms of the advantages and benefits of using log modeling and 3D geocellular property modeling-while-drilling. It is concluded that modeling-while-drilling is extremely useful in optimizing horizontal well paths, maximizing well productivity, and reducing rig lost time. In addition, it allows professionals from different disciplines, to work together in an integrated manner for improved well placement.
Thru-Tubing Gravel Pack Experiences in Malaysia
Authors: Saebi Shahryar , Rivero C. Maria Elba , Gornescu Bogdan Claudiu , Veysalli Elshan , Sepulveda Willem , Zaini Muhamad Zaki , Kikuchi Masato , Tsangueu Barbara
Published: March 2015

Thru-Tubing Gravel Pack Techniques have been receiving an increasing attention in the recent years as a cost effective solution for sand producing wells with either failed gravel packs or zones that started sand production at a later stage during the life of the well especially in mature fields with marginal reserves as the conventional workover operations are usually not economically justified. In most cases, because of the marginal reserves available and the high cost of mobilizing a workover rig to perform a conventional gravel pack completion, the operators chose to recomplete the wells using rigless techniques. This paper covers some of the applications that the gravel pack has been placed through the existing completion tubing. It will review the successful installations performed in Malaysia, including the engineering design, completion operations, real-time decisions, and results. The proposed solutions and the lessons learned in these projects could change the sandface completion practices for sand prone wells that are either shut-in or not producing up to their potential in the mature fields.
From Well-Driven Seismic Data Processing to Seismic Reservoir Characterisation by 3D Seismic Imaging of Ordovician Karst Caves in West China
Authors: Tian Jun , Lei Xue , Cai Zhenzhong , Yuan Yuchun , Han Xiaoli , Tong Yanming , Miao Qing
Published: March 2015

Accurate idenfication of oil bearing caves within Ordovician Karst carbonate formation utilizing conventional low-fold 3-D seismic data has been a rigorous challenge. We executed a well-driven seismic data processing workflow which includes prestack time migration and reservoir characterization by prestack simultaneous AVO (amplitude variation with offset) inversion for estimation of physical rock properties and postmigration multi-attribute analysis. Delineation of oil bearing caves is achieved by the interpretation of the inverted attributes, postmigration attributes, and attenuation factor analysis with angle stacks. As a result of this work, two highly productive wells were drilled which and successfully reached the target of oil bearing caves.

Background and challenges

The production is mainly from the epikarst (the uppermost weathered zone) and the caves whose scales vary from tens of centimeters to over ten meters. Drilling experience demonstrates coexistence of oil bearing, oil and water bearing, water bearing, and shale-filled caves. High drilling success rate is associated with epikarst targets while high production rate is associated with oil bearing cave targets (Fangjian Xue, 2010) in the area. High-production rate is the primary objective -for our study area.

The 3-D survey includes three blocks overlapping conventional 3-D data sets during the last fifteen years with different parameters. Normal fold in the two blocks is 24 and 72 in the third block. Based on the spectral analysis of the raw data, recoverable signal band at the target level is about 8–40 Hz in one block and 6–45 Hz in the other two blocks. The legacy seismic processing datasets show poor image with very low resolution and fair signal to noise (S/N) ratio at the target interval. Additional available data include several vertical seismic profiles (VSP), check shots and complete log measurements from dozens of wells, five dipole sonic measurements for the Ordovician and the overlain partly clastics carboniferous sections, and various well test data.

Various processing challenges (Wang et al., 2011) associated with poor acquisition and complex subsurface geology (Feng et al., 2011) affect the accuracy of the seismic image. Nevertheless, there are no significant lateral velocity variations above the target level that would require prestack depth migration. Main challenges in reprocessing the 3-D seismic data sets are (1) ensuring consistency of seismic amplitude, frequency and phase in merging the three survey data sets, (2) enhancing S/N ratio, (3) improving seismic image and relative amplitude preservation, and 4) improving seismic resolution. Additional challenges are AVO inversion and identification of fluid properties in the caves.
Air Quality Control Initiatives
Authors: Al-Ameer Hassan , Al-Alawi Hijji , Al-Balawi Abdulrahman
Published: March 2015

The intent of this paper is to share the successful operational story in controlling air quality at Saudi Aramco, Uthmaniyah Gas Plant energy efficiency program. Obligation with environmental regulations becomes, nowadays a challenge to the industry fields. UGP was committed to comply with the government and Saudi Aramco environmental standards by implementing several ideas to enhance the air quality. The first idea is Wet Hydrocarbon Recovery System which eliminates the continuous use of burn pit for Wet HC from eth blow down system and re-injects back into the HC crude lines. Beside this modification will allow UGP to comply with environmental regulations by eliminating the continuous flaring of Wet HC, it will reserve the life time of the burn pits and protect the ground water aquifer from contaminations. The second idea is upgrading the Sulfur units from CLAUS process to SUPERCLAUS process to achieve 98.7 % of sulfur recovery and reduce SO2 emissions by installing new condenser with coalser and changing the type of converters' catalysts. All of these modifications resulted in decreasing the SO2 emissions by 25 %. The third idea is Flare Gas Recovery System which the system will recover the flare gases from the flare headers and then compressed the gas to 260 psig for feeding the plant low pressure sour gas header. The ultimate goal of this idea is to avoid visible smoke and flame from flaring system and comply with environmental regulations. The system is very attractive not only reducing flares' emissions but also it would recover the valuable gases being wasted to the flare stack. This paper discusses, in details, all ideas objectives, processes and benefits.
Comprehensive Evaluation of Hull Form Design for an Icebreaking Vessel in the Kashagan Field
Authors: Putorti E. , Cijan A. , Trincas G.
Published: March 2015

Both the ice-going and structural capability were analyzed in a comprehensive way for the IBEEV, a small-sized, shallow draft icebreaker vessel, equipped with two pulling type thrusters and operated by AGIP KCO in the Kazakhstan sector of the Northern Caspian Sea. To this end, a number of activities involving Navalprogetti and Krylov Shipbuilding Research Institute was implemented, encompassing analytical and numerical computations, model tests in open water, shallow water and ice towing tanks and full-scale measurements in ice.

To evaluate performance of IBEEV all year long, the power-speed relationship was estimated in both open water and ice conditions. As regards open water, the ultra-shallow water depth showed dramatic influence on the vessel's resistance, hull-propeller interaction, and bollard pull capability. The performance in ice was analyzed through analytical and numerical models, experimental model testing and full-scale trials. The full-scale campaigns allowed determination of (i) maximum ice-breaking capability of the vessel in level ice, (ii) gyration radii of the vessel running both ahead and astern, and (iii) capability of channel break out for the vessel.

Finally, to determine service restrictions of IBEEV based on hull ice strength a number of strength criteria was identified, namely, not-exceed the service line load under normal operation; value of the ultimate strength of ice strengthening structures, and damage limits to avoid water leakage. To this end, theoretical analyses were carried out by means of the hydrodynamic model of the vessel impact against the ice. The numerical results were validated by full-scale experimental results and confirmed that IBEEV complies with given constraints.
The Eagle Ford Shale Play, South Texas: Regional Variations in Fluid Types, Hydrocarbon Production and Reservoir Properties
Authors: Tian Yao , Ayers Walter B. , McCain William D.
Published: March 2015

The Eagle Ford Shale is one of the most active U.S. shale plays; it produces oil, gas condensate, and dry gas. To better understand the regional and vertical variations of reservoir properties and their effects on fluid types and well performance, we conducted an integrated, regional study using production and well log data.

Maps of the average gas-oil ratio (GOR) of the first three production months identified four fluid regions, including black oil, volatile oil, gas condensate, and dry gas regions. Maximum oil production occurs in Karnes County, where first-month oil production of most wells exceeds 5,000 barrels (bbl). The most productive gas region is between the Stuart City and Sligo Shelf Margins, where first-month gas production of most wells exceeds 60 million cubic feet (MMcf).

Eagle Ford Shale petrophysical properties were analyzed in individual wells and were mapped to clarify the regionally variations of Eagle Ford Shale reservoir properties and their controls on fluid types and well performance. In comparison to the upper Eagle Ford, the lower Eagle Ford Shale has high gamma ray, high resistivity, low density, and long transit time values; we infer that the lower Eagle Ford shale has higher total organic carbon and lower carbonate content than the upper Eagle Ford Shale.

Integration of production and geological data shows that thermal maturity and structural setting of the Eagle Ford Shale strongly influence fluid types and production rates. Plots of GOR vs. time for individual wells were constant in different reservoir fluids. Results of this study clarify causes of vertical and lateral heterogeneity in the Eagle Ford shale and the regional extents of fluid types. Understanding of the reservoir property differences between upper and lower Eagle Ford Shale should assist with optimizing completion design and stimulation strategies. The results may be applicable to similar developing shale plays.
Saudi Arabia's Value Adding, Record-Breaking Coiled Tubing Interventions Travel Farther than Mount Everest
Authors: Arukhe James , Ghamdi Saleh , Dhufairi Mubarak , Duthie Laurie , Almari Abdulrahman , Elsherif Tamer , Othman Bassem
Published: March 2015

Coiled tubing (CT) deployment with hydraulic tractors in extended reach open hole horizontal wellbores has been a challenging technology in the oil industry for reasons ranging from wellbore conditions like washouts to restrictions imposed by the completions. Consequently, delivering cost-effective well interventions solutions, for example through acid treatments to enhance well performance, or production logging to understand inflow profiles in deep injector wells have been particularly demanding.

The authors examine how rigorous pre-job planning and teamwork were enablers to realizing the deepest CT reach at 30,365 ft (9.26 km) measured depth (+1,336 ft longer than the height of Mount Everest at 29,029 ft) in a mega-reach open hole horizontal power injector well using a CT tractor to facilitate effective stimulation in Saudi Arabia. Among the operational challenges overcome in the well was tar accumulation on the tool string including the tractor during the well intervention. The tar accumulation on the string was part of a laterally extensive high viscosity tar layer between the overlaying oil column and aquifer. From a reservoir standpoint the tar layer posed a challenge in assuring sufficient aquifer support to the oil producers because of their partial sealing nature.

The author discusses how the challenges imposed by tar restrictions and other operational concerns were overcome to ensure successful acidizing. The wells showed a marked injectivity improvement from acid stimulation thus demonstrating the benefit of informed decisions from real time fiber optic distributed temperature sensing (DTS) in fluid placement. The tractor traversed a difficult down hole environment overcoming washouts and H2S environments within the wellbore conveying the CT for an industry record tractor reach for open hole CT intervention at 30,365 ft. Concrete applications of these outcomes include the ability to employ real time information for cost-effective stimulation and real time log acquisition from extended reach open hole horizontal wells.
Overview of Key Zonal Water Injection Technologies in China
Authors: He Liu , Yang Gao , Fuchao Sun , Fangchao Liu , Xuebing Cui , Qinghai Yang
Published: March 2015

Separated layer water injection is the important technology to realize the oilfield long-term high and stable yield. Through continuous researches and technological innovations, series separated layer water injection technologies have been developed to meet the technology needs of the different oilfield development stages to solve the interlayer problems, achieve high efficient of water injection, and solve the bottlenecks in different water injection stages. Oilfield water injection gradually comes to separated layer water injection, separate minilayer water injection and fine water injection stages from the early stage commingled water injection. Water injection technologies have experienced five main stages: commingled water injection, concentric water injection, eccentric water injection, integrated water injection and intelligent water injection. Every stage of the technology has played an important role for the oil field development. With the development of the separated layer water injection strings, downhole tools and supporting testing and conditioning technologies for the separated layer water injection, separated layer water injection technology has played an important role in evenly exploiting each reservoir and improving the producing extent of the bad reservoir. This technology has realized zonal production of the multilayer reservoir, and provided the technical support for keeping the oil production from the water flooding taking up more than 80% of the total.

Introduction

Water injection is the base of oilfield development. Separated layer water injection technique has play an important role in realizing the oilfield long-term high and stable yield and improving oil recovery. And it is also the inevitable choice to maintain oil production rate for water flooding reservoirs with high water cut. In order to satisfy the needs of different oilfield development stage, a series of water injection technologies have established to handle conflicts between layers and realize water injection effectively. The water injection strings have experienced stationary separated layer water injection, eccentric water injection, concentric integrated water injection and eccentric separated layer water injection from the early stage commingled water injection. Supporting testing and conditioning technologies for the separated layer water injection have come to cable testing and conditioning, ground control downhole water choke stepless regulation from steel wire free dropping and fishing technology. After 60 years development of separated water injection and supporting testing and conditioning technology, the separated layer water injection technology has come to "eccentric separated layer water injection + cable testing and conditioning", which has improved the recovery ratio of the water injection wells as a main water injection technology in China.
Dynamic Characterisation of a Chinese Fluvial Tight Gas Reservoir
Authors: Boutaud de la Combe Jean-Luc , Jaffrezic Vincent , Loizel Herve
Published: March 2015

South Sulige block, located in the Ordos Basin in China, is classified as Tight Gas Reservoirs with permeability ranging from 0.01 md to 2 md and porosity rarely exceeding 10%. Potential gas production intervals were identified in the Shihezi Formation and Shanxi Formation.

Four of the existing hydraulically fractured wells, were re-tested by Total.

Total drilled four new wells on this block, stimulated them with hydraulic fractures and performed extensive tests.

The main objectives of well testing were:To reduce the uncertainties on well productivity, mainly permeability and skin.To characterize reservoir extension: no flow boundaries, channel width.To estimate the dynamic connected volumes which are linked to the extent and interconnectivity (amalgamation) of the sand bodies (fluvial sand bars/channel width).

Extended dual build-up tests were designed (from 8 to 18 months) ended by a long duration build-up (from 3 to 10 months) to characterize well productivity and connectivity. As no signature of radial flow, appeared on derivatives, permeability-thickness values were strongly uncertain. Dual build-up tests were designed to allow us to reduce uncertainties on permeability-thickness product. The test analyses have revealed the presence of channel margins to match transient depletion between build-ups.

The results of these extended tests highlighted that channel widths determined by pressure transient analysis were much smaller than expected, compared to outcrop description, except for one well (Y3). This implies that internal heterogeneities, not visible on outcrops, play a major role in the well drainage. These results have to be taken into account to optimize the development scheme, combining the good productivity in the Y3 area and more standard well behaviour elsewhere.
The Distribution Controlling Factors of Reef and Shoal, and Their Favorable Plays Analysis: Changxing(Permian)-Feixianguan Formations(Triassic),Sichuan Basin
Authors: Long Wen , Yu Yang , Qi Zhang , Yi Liu , Xian Zeng Yun , Liang Xu
Published: March 2015

Reef and shoal gas reservoirs in the Permian-Triassic Changxing-Feixianguan formations, Sichuan Basin, are typical representative of the marine carbonatite gas reservoirs in china. Breakthroughs in exploration make it necessary to know the distribution controlling factors of reef and shoal. Based on the comparative analysis of various well data and 3D seismic, the impact of various factors is studied on the distribution of reef and oolitic shoal, such as the geometry of the Kaijiang-Liangping trough, Late Permian regional palaeogeomorphologic framework, tectonic extension, system tracts of the Longtan-Feixianguan formations. The following conclusions were drawn. (1) At the end of Late Permian, the palaeogeomorphologic framework of the Sichuan Basin was "three depressions separated by three uplifts" which played a key role in controlling the distribution of reefs and oolitic shoals. (2) Transgressive systems tract (TST) deposits dominated the Longtan-early Changxing period, mid-late Changxing period has a highstand system tract (HST) deposits feature. Highstand system tract (HST) deposits dominated Feixianguan period. The change of system tracts made it possible to develop multistage reefs near the platform margin. Oolitic shoals may occur on the progradation slope margin in the Kaijiang-Liangping trough, while the aggradational platform margin is the most favorable development zone of Oolitic shoals. (3)The unevenness of extension caused the differences in the development of platform margin palaeogeomorphologic, which influenced the development time, continuity and their superimposed relationship of reef and oolitic shoal. (4)The methods, based on 3D seismic, are studied for characterizing the bioherms distribution along the platform margin. The distribution and shape of Bioherms along the platform margin can occur as curved belt, moniliform and atoll, or occur as echelon belt oblique to the platform margin. Favorable Plays are analyzed based on the study results.
Seismic Velocity Uncertainty Analysis In An Underexplored Basin
Authors: Bacenetti R. , Andreoletti C. , Capponi G. , Martera M. Della
Published: March 2015

In areas characterized by complex geology, Depth Velocity Analysis is the mandatory instrument to estimate the sharp velocity variations that can be expected; seismic data and processing tools are necessary but not sufficient ingredients for successful depth imaging results, so sound a priori information must be retrieved from well information and from the geological knowledge of the area of study, as well as a close integration between the geophysical and geological contexts. A proper estimation of seismic velocities is not only fundamental to obtain good imaging quality and correct depth positioning, but it can also be a key input for detecting the presence of overpressures: usually, overpressured areas are associated with seismic velocity inversions. Moreover, in areas where anisotropy is unknown because of lack of well information, seismic velocities are affected by uncertainty: this must be taken into account in order to quantify the consequent uncertainty both in depth positioning of the target and in pore pressure prediction. In this paper a case history from Offshore Ghana is presented, dealing with the above mentioned issues: the intimate correlation that exists between anisotropy and velocity analysis is investigated, and the impacts of the uncertainty that affects them is considered.
Geological Interpretation of a Weakly Confined Channel Complex Integrating Seismic Amplitudes and Elastic Inversion Attributes (Offshore Ghana)
Authors: Care Davide , Cavanna Giorgio , Capponi Giulia , Fonnesu Franco , Knezaurek Gabriella , Piva Andrea , Torricelli Stefano
Published: March 2015

During the last decade, seismic-based studies have become fundamental for detailed and objective descriptions of reservoir depositional elements, a necessary condition for building robust stratigraphic frameworks and sedimentological interpretations unbiased by questionable analogues or existing models. A close integration of sedimentary geology and geophysical interpretation is presented here to demonstrate that these two disciplines can support each other to provide a powerful tool for predicting reservoir sandstones architecture.

The work was carried out on the deep-water sequences of the Ghanaian offshore, which have been interpreted as weakly confined channel complexes (WCCC) deposited at the base of slope. WCCC are approximately 150–300m thick and 10–15km wide and made of stacked, laterally amalgamated channels and lobes vertically separated by shale-prone intercalations.

Detailed interpretation of individual seismic reflections followed by an elastic inversion and Bayesian facies classification calibrated with 3 wells allowed to identify several distinct small-scale composite channel fills and lobes forming sand bodies 1–2km wide and 15–25m thick. High and low-sinuosity sand bodies compensate each other and stack vertically, migrating progressively from West to East. Furthermore, some channel-fills show a marked aggradational pattern. The overall depositional pattern is believed to represent a progressive decrease in sediment supply leading to the de-activation of the system.

Despite the key sand bodies were correctly identified on seismic amplitudes and well-logs through conventional, "qualitative" approaches, their subsequent "quantitative" imaging by elastic inversion and facies (shale, brine and gas) probabilities allowed to clarify many uncertainties in the stratigraphic and sedimentological framework, particularly where the marked AVO fluid effect inevitably interfered with the initial, purely sedimentological interpretation. High-res biostratigraphic data further confirmed the inferred physical-stratigraphic and litho-fluid framework established through the integration of seismic sedimentology and quantitative geophysics.
Evaluation of Chelating-Hydrofluoric Systems
Authors: Al-Harbi B.G. , Al-Khaldi M.H. , Al-Dahlan M.N.
Published: March 2015

Different chelating agent-HF mixture systems have been used to stimulate deep hot sandstone formations. Typically, chelating agents are used as a substitute for HCl and organic acids in HF based systems to stimulate hot and exotic oil and gas sandstone formations. Apart from reducing the risk of corrosion, secondary and tertiary reactions, the system can be deployed in formations containing high clays and carbonates as well as iron and zeolite bearing sandstone formations. However, several fields' cases indicated precipitation of aluminum-based scale following acid treatments that include these systems. The focus of this paper is to identify the type of precipitations that occur during the reaction of chelating-HF systems and determine the factors that affect these precipitations.

Solutions of different ethylenediaminetetraacetic acid EDTA containing two ammonium bifluoride ABF concentrations of 0.5 and 1.0 wt% were examined in this study. Aluminum chloride or calcium chloride was added separately to each chelating-HF solution to contain various concentrations of aluminum or calcium. The filtered liquid was analyzed using inductively coupled plasma ICP, while formed solid precipitate was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

The main type of precipitate in solutions containing aluminum was identified as AlF3. The amount of precipitate was found to be dependent on solution initial aluminum and free fluoride concentrations. In other words, the main factor that controlled the aluminum-fluoride precipitation was found to be F/Al ratio and above a critical F/Al value, AlF3 precipitates.

Introduction

Hydrofluoric based acids have been extensively used to stimulate sandstone formations with variable success rate. The poor results are mainly attributed to the rapid spending rate, subsequent precipitation, and decomposition of sensitive clays and matrix unconsolidation (Smith and Hendrickson, 1965; Gidley, 1985; Brady et al., 1989; Simon and Anderson, 1990; Shuchart, 1995; Gdanski and Shuchart, 1996; Thomas et al., 2001). Hydrofluoric based acids went through several optimization and development processes to overcome these potential limitations and the main drivers were developing acidizing fluids with low corrosivity, retarded reaction rate and without undesirable reactions by-products (Rae and Di-Lullo, 2003). In terms of regular mud acid, in order to avoid undesirable reactions by-product, HCl/HF ratio is recommended to be maintained high i.e. 9/1 (Gdanski and Shuchart, 1996). Nevertheless, strong acids such as HCl decompose sensitive clays i.e. illite and chlorite by extracting aluminum resulting in amorphous silica precipitation and fines migration (Simon and Anderson, 1990; Thomas et al., 2001).
Geomechanical Technology for Seal Integrity Analysis: The Three-Step Approach
Authors: Davison J.M. , van den Bogert P. , Schutjens P. , Ita J. , Fokker P.
Published: March 2015

A clear understanding of the subsurface pore pressure and the presence of geological seals are significant considerations when designing safe wells and optimal production strategies for oil and gas resources. This paper highlights geomechanical techniques and tools which have been developed to assure injection operations for large scale EOR projects in South-East Asia. A key concern is if depletion or injection will lead to reservoir or seal failure by tensile fracturing or shear faulting. If so, will these fractures and faults "grow" upwards and provide a pathway for fluids to escape to the seafloor? First, a 1D-model is made of the total stresses and pore fluid pressures and how these change as a function of depth and depletion/injection. This empirical approach helps to highlight the zones of relatively low minimum effective stress where there is greater risk of rock deformation which will impact operations. Where more detail and refinement is required in terms of the identified risks, we analytically describe the reservoir and overburden deformation with the theory of poro-elasticity, Mohr-Coulomb-type shear faulting, and tensile fracturing. Analytical geomechanics aims at a mechanistic understanding using simplified geology and simplified pore pressure patterns, but with realistic mechanical rock properties. The third step delivers greater detail of the technical complexity using a 3D finite-element simulator. These numerical techniques can simulate the effects of complex structural geology or intra-reservoir compartmentalization, inhomogeneous depletion, and spatial variation in rock mechanical properties. It makes sense to start simple and gradually bring in more complexity whilst adjusting geomechanics support accordingly. We demonstrate the above three-step approach with examples from projects in the South China Sea, offshore Malaysia, which illustrate the multi-disciplinary aspect of geomechanics and its impact on safety, efficiency (costs), and the technical reputation of our company and industry.
Optimal Infill Drilling Using Simulation and Cross-Functional Integration-Ubit Field Example
Authors: Krukrubo G.J. , Nwakwue J.E. , Babafemi O.A. , Young R.H. , Ogunnusi H.O.
Published: March 2015

The Ubit Field, located southeast of the Niger Delta, is a Nigerian National Petroleum Corporation (NNPC)/Mobil Producing Nigeria (MPN) Joint Venture (JV) asset that has been on production for more than 40 years (September 1970). Ubit has approximately 2.4GBO OOIP, with production peaking at ~137,000 BOPD in 1997, and is currently at ~85,000 BOPD. With much of the reserves yet to be produced, it is important that an optimized field development plan be implemented to maximize recovery. Guided by reservoir simulation models, a revised Ubit Field re-development plan was approved in December 2009. Infill development has proceeded as designed, and the first infill drilling program is underway.

Integration of results from reprocessed seismic, geologic interpretation, core, log and reservoir simulation studies, coupled with state of the art technology in well completions, were critical in developing an optimized depletion plan. Reservoir simulation results consistently indicate higher reserves capture with increased well density from infill drilling that targets unswept locations around and down-dip of abandoned completions. Results from the integrated studies suggest varying the optimum well spacing requirements for the different sections of the reservoir. The recovery factor in the lower quality reservoir section (Disturbed Biafra) could be vastly improved by increasing well density.

The multidisciplinary study for field development indicates that approximately 100 additional wells should be drilled to tap unswept resource in the field. This aggressive approach will maximize ultimate recovery, but requires closer well spacing than minimum regulatory specification. The technical basis for this strategy, primarily reservoir simulation models anchored in measured hard-data, is the core focus of this paper.
Variable Nozzle-Based Inflow Control Device Completion: Inflow Distribution Comparison, Analysis, and Evaluation
Authors: Abd Elfattah Mahmoud , Al-Yateem Karam , Qahtani Hassan , Rajabian Behzad
Published: March 2015

This paper presents a study of horizontal well completions equipped with inflow control devices (ICDs) in a large, unconsolidated sandstone reservoir in Saudi Arabia. The focus is the improved production performance gained through a completion using ICDs with variable nozzle settings across the openhole section vs. that from a cemented, perforated liner completion and uniform nozzle setting ICD completion performance. Discussion includes an overview of ICD and intelligent completions and their components, and the advantages and limitations of both uniform/variable types of ICDs completion design methods. Results from two wells in Saudi Arabia show that the major advantages of completions using ICDs with variable nozzle settings are the operator's ability to make adjustments at the wellsite; to balance the inflow from areas of differing permeability; to reduce the pressure drop across the completion; and to better controls water production compared with uniform nozzle setting ICD completion.

Inflow Control Device (ICD) technology has been developed to overcome horizontal well production/injection challenges. ICD completion with packers segregates openhole (OH) horizontal section into compartments to balance inflow/outflow along the well and control undesirable water/gas production.

There are various types of ICDs such as tube, helical, orifice and nozzle ICDs. The advantages of orifice/nozzle ICDs (Fig. 1) are their viscosity independence and the nozzle installation at the wellsite according to the attained while drilling properties/openhole logs that might change ICD completion design optimization. The optimum ICD completion is one which balances influx from heterogeneous reservoirs and control water/gas production and simultaneously without creating a huge pressure drop across the completion.
Safety Enhancements Using Wireless Technology in Gas Plants
Authors: Al-Hashim Najeeb S. , Al-Deraa Abdulrazaq H.
Published: March 2015

The motive force behind this advanced concept in implementing "Wireless Technology Using Solar Powered" instruments is to get hydrogen sulfide (H2S) and lower explosive level (LEL) signals from an unreachable location where hazardous waste is being handled to a safe centralized control room. Implementing this would reduce the cable cost and the maintenance. This solar power is eco-friendly. With wireless communication, allowing more sophisticated data to be transmitted to the centralized control room; appropriate steps have been taken to install wireless devices in remote location. Such technology plays a progressively essential role in up-to-date industries. The wireless solar powered sensors provide a cost-effective alternative and are being used increasingly for equipment and other applications in a diversity of industrial processes. In addition, its improved remote diagnostics makes plants and operations safer. In this paper, we will cover the benefits and challenges we experienced at the Haradh gas plant while implementing wireless technology to prevent massive threats and destruction to persons, property and equipment.

Introduction

Wireless technology has been growing exponentially over the years. Consequently, wireless technology developments are providing numerous advantages in gas plants and the operating plans for refineries. These developments are providing new opportunities for enhancing plant performance, reliability and safety while reducing installation and maintenance/operating costs. In Saudi Aramco's business, the safety of employees is at the top of its priorities. Since the lower explosive level (LEL) gas or hydrogen sulfide (H2S) could be present in most of Saudi Aramco's operation facilities, it is mandatory to install LEL/H2S sensors in every location where the hazardous gases are expected. For gas plants and refineries there are a lot of challenges related to monitoring H2S and LEL gas releases. The biggest challenge for monitoring releases of gas in plants is to cover isolated remote field locations such as the oily sumps area outside the plant fence. To overcome this challenge, a new solution was designed to fit this application. This solution can be achieved by installing standalone wireless H2S and LEL detectors powered by solar cells plus batteries, beacon and horn. The system consists of different equipment that is using Saudi Aramco standards as well as international standards. The International Society of Automation (ISA) standard for wireless systems - Process Control and Related Applications - is ISA 100.11a [3, 5].

This paper reviews the use of H2S and LEL solar powered wireless sensors for safe operation in gas plants and refineries. The paper also addresses the system design and integration.
Drill Pipe Riser Intervention System Successful Experience in Offshore West Africa
Authors: Rohart Christophe , de Fonvielle Henri , Bordet Laurent , Campbell William , Susak Nenad
Published: March 2015

While offshore intervention on subsea equipments is quite common, the increasingly deeper water operations require light weight intervention systems while meeting safe and stringent operating specification. For these new deep offshore challenges, the conventional risers are becoming a more costly and less desirable solution.

Starting with a recollection of the main drivers that motivated the development of drill pipe riser intervention systems (DPRIS[i]), the paper details the technical and economical challenges in West Africa that have led to the design of such a solution. When non productive time and financial aspects are taken into account, it makes sense to develop a dedicated system in order to provide fast and reliable intervention.

Depending on the field requirements, two different types of drill pipe riser systems using a proprietary double shoulder connection were used by operators. A first solution was developed in 1999 featuring a seal ring close to the external shoulder. Subsequently, a new solution featuring a gas-tight metal to metal seal on the pin nose was developed in order to address increasingly demanding and challenging operations.

Intensively used in West Africa since 1999, the solution using the seal ring has shown robustness and reliability while being used for several projects in Angola such as Girassol and Rosa and now GirRI. The paper draws a summary of these operations and the feedback on the field use and maintenance. Also it emphasises the successful qualification process for the metal to metal seal solution that has been used in offshore Nigeria since 2010 for the USAN project.
Imaging Velocity of Pre-Stack Depth Migration in Steep and Complicated Structures
Authors: Xiaoyun Dai , Xiaoxia Luo , Tiemin Wen
Published: March 2015

During the processing of pre-stack depth migration (PSDM) of seismic data in complex structures in western China, an anomaly of interval velocity inconsistent with geological features appears, even when the CRP gather is flattened and the residual velocity (or the residual moveout) returns to zero(Reshef, 2001). The model data analysis in this paper suggests that velocity errors in the shallow layer lead to these anomalies. In order to improve PSDM results of near-surface complicated zones, the velocity variation trend of the deep layer is restrained by geological constraints and residual spectra and afterwards an updated velocity modeling method using the corrected shallow layer velocities is applied. The crucial point in this paper is to understand the reasoning for velocity anomalies and to build a relatively correct velocity model using the PSDM velocity analysis.

Introduction

The pre-stack depth migration technique has recently been widely used to obtain better structural images of overthrust nappes in the piedmont zone of western China. Since the surface conditions are complex, poor shooting and receiving conditions result in a low signal-to-noise ratio (SNR) of seismic data and as a result, it is hard to identify effective seismic reflection information of shallow layers data. The very low SNR makes PSDM velocity modelling difficult.

The PSDM velocity model is derived from the initial interval velocity by velocity iteration and the interval velocity is converted from pre-stack time migration (PSTM) RMS velocity according to the DIX formula. Whether the iteration velocity is correct or not depends on if CRP gathers are flattened and reflection stack energy reaches a maximum. Using this rule, the accuracy of picking velocity is not guaranteed when CRP events can't be identified. There are more picking velocity errors of shallow layers in continental piedmont zone. The main reason is that piedmont lithology and the velocity of shallow layers is various in transverse and longitude. At the same time, the precision of the velocity spectrum is affected by poor shooting and receiving conditions, less valid multiple stacks and a low SNR of shallow seismic data. This paper focuses on the deep velocity error of complex structures affected by incorrect shallow velocity models that may cause structural deformation of PSDM results.