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Understanding rock properties and how they react under various types of stress is important to development of a geomechanical model before drilling. Some major geomechanical rock properties are described below. To first order, most rocks obey the laws of linear elasticity. In other words, the stress required to cause a given strain, or normalized length change (Δlk /ll), is linearly related to the magnitude of the deformation and proportional to the stiffnesses (or moduli), Mijkl. Furthermore, the strain response occurs instantaneously as soon as the stress is applied, and it is reversible--that is, after removal of a load, the material will be in the same state as it was before the load was applied.
Abstract Short radius wells typically incorporate build rates between 35deg per 100ft and 70deg per 100ft. These wells are typically drilled to minimize exposure of a problematic zone above the target or to reduce geological uncertainty. This paper will discuss best practices and equipment developed specifically for delivering these wells in the Middle East. Case histories will illustrate the close collaboration with the operator resulting in performance step change for short radius drilling. The approach is based on a rigorous Drilling Engineering process. Such process is divided in four major steps; design, execute, evaluate and optimize. One of the first key steps is to perform a diligent risk assessment ensuring the customer objectives are achieved. This resulted in the development and implementation of technological innovations on downhole motors and Measurements While Drilling (MWD) tools to achieve the required high build rates safely and consistently. Proper communication was crucial for flawless execution, and meticulous documentation enabled proper evaluation and optimization of the art of short radius drilling. For over 10 years, multiple short radius wells have been consistently delivered meeting their objectives; from successful sidetracking operations, accurate curve landing, optimum geo-steering, valuable Logging While Drilling (LWD) data collection, to extending the life of the wells by maximizing their production. The last two steps of the Drilling Engineering cycle (evaluate and optimize) have been the foundation of the continuous improvement process; targeting adequate equipment maintenance, Bottom Hole Assembly (BHA) design and operational practices to ensure consistent results. The paper will recap the drilling engineering cycle for wells drilled recently. The discussed best practices have enabled master the art of short radius drilling. Such distinctive knowledge should be shared with the entire oil and gas industry. The paper captures the engineering approach to tackle the traditional challenges of drilling short radius wells. It also discusses the reliable solution for drilling short radius wells in Middle East which are planned to access new reserves from an existing infrastructure, while minimizing drilling and geological risks.
AlGhamdi, Sarah Mohammed (Schlumberger Oman) | Beche, Amina (Schlumberger Oman) | Awadalla, Muhannad (Schlumberger Oman) | Naamani, Hafidh (Petroleum Development Oman) | Aljiroudi, Fadi (Petroleum Development Oman) | Hashemi, Alkhalil (Petroleum Development Oman) | Siyabi, Khalid (Petroleum Development Oman) | Hooti, Younis (Petroleum Development Oman)
Abstract Drilling long laterals within Shuaiba limestone reservoir without exit to Nahr-Umar shale in the challenging field "B" that is characterized by geological uncertainty can have major risks. The low to very low resistivity environment reservoirs are common in Oman especially while placing wells nearby OWC; on a reservoir spot window of 1-2m TVD only. The main objective is to place the well less than 1m TVD below the reservoir top, this was achieved by utilizing Multilayer Bed Boundary Detection and Rotary Steerable System. Integrating propagation resistivity curves response with the directional resistivity curves response from Bed Boundary detection tool have been used as a guide for an optimal well placement in low resistivity reservoir, along with Rotary Steerable System are one of the best strategies which have been used to place the wells within the right spot. For tight geosteering window with an aggressive formation tendency pushing the azimuth left or right and continues inclination instability associated with the existence of an interbedded layers of hard streaks within the reservoir, a faster and more competent Rotary Steerable System tool and Bit selection is required, as proven it provides better stability results for achieving well placement objectives and respond in fast manner to geosteer in real time. The objective of this paper is to describe the geosteering logging while drilling (LWD) technology and technique and Rotary Steerable system (RSS).
Abstract Assessment of effective mechanical properties such as elastic properties and brittleness can be challenging in the presence of complex rock composition, pore structure, and spatial distribution of minerals, especially in the absence of acoustic measurements. Conventional methods such as effective medium modeling, are not reliable for assessments of mechanical properties in complex formations such as carbonates, because solid skeleton of carbonates does not consist of granular minerals with ideal shapes. The effective medium models also overlook both the spatial distribution of petrophysical properties, and the coupled hydraulic and mechanical (HM) processes, which causes significant uncertainties in geomechanical evaluations. The objective of this paper is to develop a numerical method to enhance assessment of effective mechanical properties of anisotropic and heterogenous carbonate formations by modeling the variation of effective stress and the evolution of corresponding strain. The developed method takes into account the coupled HM processes, the realistic spatial distribution of rock inclusions (i.e., rock fabrics), dynamic fluid flow, pore pressure, and pore structure. To achieve this objective, we develop a pore-scale numerical simulator by satisfying conservation equations and considering the coupling among relevant HM phenomena. We adopt peridynamic theory to discretize the micro-scale medium. The inputs to our numerical modeling include pore-scale images of rock samples as well as mechanical and hydraulic properties of each rock inclusion. We perform image processing on micro-CT scan images of rock samples to obtain a realistic micro-scale structure of both rock matrix (i.e., concentration, spatial distribution, and shape of rock constituents) and pore space. We then assign realistic mechanical and hydraulic properties to each rock constituent within the pore-scale medium. The outcomes of numerical modeling include the variation of effective stress and the evolution of corresponding strain by honoring the variability in mechanical/hydraulic properties of rock inclusions caused by their spatial distribution, pore pressure, pore structure, natural fractures, and dynamic fluid flow at the micro-scale domain. We then compare the outcomes of numerical models with the mechanical properties estimated based on effective medium models.
Saleh, Khaled (Schlumberger) | Morad, Aly (Schlumberger) | Cavalleri, Chiara (Schlumberger) | Hakim, Emad Abdel (General Petroleum Company) | Farouk, Mohamed (General Petroleum Company) | Atwa, Eslam (General Petroleum Company) | Ameen, Mohamed (General Petroleum Company) | Youssif, Youssif (General Petroleum Company) | Mamdouh, Kareem (General Petroleum Company)
Abstract Recent advancement in logging technology and data analytics allows measuring a comprehensive set of formation petrophysical properties and rock composition in cased boreholes. State-of-the-art pulsed neutron logging technology and processing algorithms record capture and inelastic elemental spectroscopy for matrix parameters, and detailed mineralogy characterization, total organic content estimation, and carbon/oxygen analysis, simultaneously with formation sigma, neutron porosity, and fast neutron cross-section. The fast neutron cross-section (FNXS) is a new formation nuclear property introduced by the advanced pulsed neutron tool that is independent of thermal and capture cross-section and highly sensitive to gas regardless of hydrogen index. Unlike thermal neutron capture cross-section, for which certain isotopes have extremely high values (such as Cl, B, and Gd), fast neutron cross-sections of all isotopes are more or less similar. Thus, FNXS is approximately proportional to atom density. Therefore, this new nuclear property has functionality similar to that of the bulk density (gamma-gamma density measurement). A local relationship can be defined to convert the FNXS into bulk density when the lithology and fluid properties are known, and calibration is possible. Otherwise, a more comprehensive assessment of bulk density can be performed by integrating FNXS with the other outputs from the slim pulsed neutron logging into a mineral solver. While solving for rock and fluid volumes from the cased-hole logs, a reconstructed bulk density may be derived in a cased-hole environment. This synthetic bulk density can be used by geophysicists to develop synthetic seismograms to properly map formation tops with surface seismic data. Since the pulsed neutron measurements follow linear volumetric law equations, they can be directly integrated into a mineral solver together with the elemental spectroscopy outputs to create a synthetic bulk density, together with the other answers. A blind comparison was done between synthetic bulk density from the cased-hole log-based mineral solver and a measured openhole density, showing a strong correlation in a three-phase fluid reservoir (gas, oil, and water). A synthetic seismogram is an essential tool when geophysicists fine-tune surface seismic data. This seismogram is developed using bulk density and compressional slowness to derive acoustic impedance, where sometimes bulk density is missing. As a result, an old approach to estimate bulk density using Gardner’s equation has certain limitations in complex environments. The new formation nuclear property that is now available in the slim pulsed neutron technology can be leveraged to provide a more robust and quality-controlled synthetic bulk density derived through FNXS integrated with the other pulsed neutron and spectroscopy outputs.
Alkinani, Husam Hasan (Missouri University of Science and Technology) | Al-Hameedi, Abo Taleb Tuama (Missouri University of Science and Technology) | Dunn-Norman, Shari (Missouri University of Science and Technology)
Abstract Lost circulation and problems related to drilling present a major challenge for the drilling industry. Each year, billions are spent to treat these problems. There is not a single solution to lost circulation because of the complexity and kind of formations susceptible to this issue. Lost circulation treatment data for the Shuaiba formation (induced fractured formation) were gathered from drilled wells in Southern Iraq (over 2000). Treatments have been grouped according to the volume of mud loss as complete, severe, and partial loss remedies. Detailed costs and probabilities calculations were conducted. The costs of three types of loss treatments (partial, severe, and complete) were handled separately since some treatments of severe, and all treatments of complete losses have to be introducing through open end drill pipe (OEDP). Expected monetary value (EMV) and decision tree analysis (DTA) were utilized to choose the optimal mud loss pathway to treat the lost circulation type. In this study, probability and cost were both considered to select the practical and efficient strategy of stopping mud loss. Too many of the remedy scenarios were investigated. The selection of the optimum strategy for every type of loss was based on the lowest EMV and efficiency. Once both conditions were satisfied, the treatment strategies were selected to treat each type of loss. Treatment strategies were provided for complete, severe, and partial losses as flowcharts that can be utilized as a reference in the field to stop or at least mitigate this troublesome problem. The methods used in this paper have the possibility to be adopted and invested to treat mud loss based on historical data of treatments in any formation worldwide.
Gianotten, Ingrid P. (Lundin Energy Norway AS) | Rameil, Niels (Lundin Energy Norway AS) | Foyn, Sven E. (Lundin Energy Norway AS) | Kollien, Terje (Lundin Energy Norway AS) | Marre, Julio R. (Miramar Julio Marre) | Looyestijn, Wim (PanTerra Geoconsultants B.V.) | Zhang, Xiangmin (PanTerra Geoconsultants B.V.) | Hebing, Albert (PanTerra Geoconsultants B.V.)
The main Petrophysical challenges in carbonate reservoirs are often to define meaningful rock types, then to establish robust permeability and saturation models for these rock types, as well as to develop a realistic estimation of irreducible water saturation (Swirr). Realistic Swirr estimation is important for predicting production behavior (expected development of water cut) and thus ultimately for planning the future development scheme of a discovery. In this study, we present the 2014 Alta discovery, located in the southwestern Barents Sea. More than 50% of the expected hydrocarbon resources reside within complex carbonate reservoirs of Permo-Carboniferous age that display highly variable rock properties. The initial screening revealed that primary rock textures and pore geometries were, for a large part, overprinted by diagenetic processes. Hence, better control on the reservoir’s diagenetic evolution will be needed to apply a full-scale rock typing workflow. In the meantime, it was decided to proceed with a simplified reservoir characterization approach based on the main stratigraphic building blocks. Sufficient core coverage allowed for using permeability measurements on core samples as direct input to a 3D reservoir model. A customized core analysis program, using whole-core samples, was designed to characterize the effect of large-scale vuggy pores. For modeling water saturation, a workflow based on the Thomeer hyperbola was developed that describes mercury injection capillary pressure (MICP) curves. The results adequately specify the saturation in all the stratigraphic building blocks. However, saturation uncertainty in the reservoir is high due to a highly variable cementation factor (m), unknown wettability, and the presence of residual oil below the current free-water level (FWL). The Alta structure has been and still is leaking gas, causing the FWL to rise over time. To address the otherwise underestimated volumes in the transition zone above the current FWL, a deeper pseudo-FWL was created and used as input to the saturation height function. Despite log-based water saturation (Archie) and core measurements (Dean-Stark) indicating more than 80% water saturation for less permeable reservoir rocks within the oil leg, production tests did not produce water at normal rates. This clearly demonstrated the need to distinguish “nonproductive” pore systems (with capillary-bound fluids; in this case, water) from pore systems contributing to production (“free” fluids). A large MICP data set confirmed that most reservoir rocks exhibit a mix of different pore types and pore-throat diameters. To model this accurately, porosity partitioning in nonproductive microporosity and movable porosity using the NMR logs was performed. Calibrating appropriate T2 cutoffs by matching core MICP to NMR logs in these heterogeneous rocks is seriously hampered by the large difference in sample size. Applying both MICP and NMR measurements to a subset of core plugs helped to resolve this challenge. Comparing the corresponding movable (“free”) porosity to total porosity revealed near-linear relationships for different reservoir rocks. For irreducible water saturation (Swirr), Swimmobile is calculated using the NMR-based movable porosity. Swimmobile is considered to be a close approximation of Swirr. The resulting full-field simulation showed a significantly improved match between model output and recorded well test data.
The INPEX-led Ichthys LNG project in Australia was recognized by the 2021 International Petroleum Technology Conference (IPTC) Excellence in Project Integration Award, which highlights projects with budgets of at least $500 million that have demonstrated distinction throughout the entire exploration and production value chain. The announcement was made during the 2021 IPTC Opening Ceremony on 23 March. The award is given to a project that adds value to the industry and exemplified strong teamwork, solid geoscience knowledge, reservoir and production engineering acumen, determined and watchful construction, and outstanding facilities engineering practices. Ichthys is ranked among the most significant oil and gas projects in the world. A joint venture between INPEX group companies (the operator), major partner Total, and the Australian subsidiaries of CPC Corporation Taiwan, Tokyo Gas, Osaka Gas, Kansai Electric Power, JERA, and Toho Gas, Ichthys LNG is expected to produce 8.9 mtpa of LNG and 1.65 mtpa of LPG, along with more than 100,000 bbl of condensate per day at peak.
Abstract Maintaining zonal isolation is vital to well economics and productive life. Well integrity is becoming more challenging with the drilling of deeper, highly deviated, and horizontal wells worldwide. Oil companies are focused on to enhance the well productivity during drilling long horizontal wells in a harsh environment by achieving maximum accessible reservoir contact. These wellbore geometries incorporate additional challenges to design and deliver a dependable barrier. In this paper, a case study about cementing the longest liner across Khuff-C reservoir has been presented discussing the main challenges, engineering considerations, field implementation, results, and conclusions. The well was drilled horizontally across Khuff-C carbonates using oil-based drilling fluid. The 5-7/8-in open hole section was planned to be cemented in single stage, utilizing 8370 ft of a 4-1/2-in liner. Careful attention was paid to estimate the bottom hole circulating temperature, using the temperature modeling simulator. A 118-lbm/ft3 slurry was designed to keep the equivalent circulation density intact. Gas migration control additives were included in the slurry design to lower the slurry's transition time, in order to reduce the chances of gas migration through the cement slurry. The slurry was batch-mixed to ensure the homogeneity of the final slurry mixture. A reactive spacer was designed to improve the cement bonding from long term zonal isolation perspective. Additionally, the spacer was loaded with optimum amounts of surfactant package to serve as an aid to remove the mud and to water-wet the formation and pipe for better cement bonding. Centralizers placement plan was optimized to allow around 63% average standoff around the pipe, staying within the torque and drag (T&D) limits. The cement treatment was performed as designed and met all zonal isolation objectives. The process of cementing horizontal liners comes with unique procedures. There are several challenges associated with carrying out wellbore zonal isolation for primary cementing of horizontal liners, therefore, a unique level of attention is required during the design and execution stages. The slurry design requires careful formulation to achieve the desired specifications while ensuring its easy deployment and placement in the liner annulus. By planning in advance and following proven techniques, many of the problems associated with the running and cementing of deep and long horizontal liners can be alleviated. This paper highlights the necessary laboratory testing, field execution procedures, and treatment evaluation methods so that this technique can be a key resource for such operations in the future. The paper describes the process used to design the liner cement job and how its application was significant to the success of the job.
Abstract Gas is envisaged as the fuel of choice in the power sector and is ideal for helping to transition toward clean, sustainable, and affordable energy access. As vital as gas is for electricity generation, the petrochemical industry, the transportation sector, and heating, many oil operators either flare or vent associated gas, a by-product of oil extraction, at the wellhead or gathering stations. Gas flaring releases greenhouse gases (GHGs) into the atmosphere. It occurs for various reasons, including infrastructure and financial constraints to capture the gas, inadequate regulatory frameworks, or binding contractual rights. The World Bank estimated the amount of flared natural gas in the oil and gas industry reached 5.1 trillion cubic feet (tcf) in 2018 (World Bank 2018). The amount of energy lost due to flaring or venting this gas is equivalent to more than 770 billion kilowatt-hours (kWh). It releases more than 310 million tonnes of carbon equivalent. Many countries and oil operators have managed to mitigate gas flaring and venting across their oil and gas value chains due to these troubling statistics. One such example is the Kingdom of Saudi Arabia. Before 1975, the Saudi oil and gas industry flared or vented over 4 billion standard cubic feet (SCF) of associated gas, a by-product of oil extraction. The flaring intensity would have increased had it not been for the construction of Saudi Arabia’s Master Gas System (MGS). The Kingdom’s gas flaring mitigation process is a successful case study of how governments and oil operators can collaborate to eliminate gas flaring by developing a domestic market for gas and enhancing the value of natural gas resources. It also demonstrates the successful transition that the kingdom had in the past five decades to achieve zero flaring through technology deployment and advancing the "reduce" component of the circular carbon economy. This paper discusses Saudi Arabia’s progress in gas flaring, the measures the government has taken thus far, and how operators have adapted to them. It also identifies many lessons learned and technological solutions that could be scaled up on a national or a corporate level to reduce gas flaring towards achieving zero routine flaring targets, especially in cases where the state owns hydrocarbon assets and leases them to private operators.