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Reservoir engineers use relative permeability and capillary pressure relationships for estimating the amount of oil and gas in a reservoir and for predicting the capacity for flow of oil, water, and gas throughout the life of the reservoir. Relative permeabilities and capillary pressure are complex functions of the structure and chemistry of the fluids and solids in a producing reservoir. As a result, they can vary from place to place in a reservoir. Most often, these relationships are obtained by measurements, but network models are emerging as viable routes for estimating capillary pressure and relative permeability functions. Before defining relative permeability and capillary pressure, let us briefly review the definition of permeability. Permeability represents the capacity for flow through porous material. It is defined by Darcy's law (without gravitational effects) as ....................(15.1) Darcy's law relates the flow rate q to the permeability k, cross-sectional area A, viscosity μ, pressure drop ΔP, and length L of the material. High permeability corresponds to increased capacity for flow. The dimensions of permeability are length squared, often expressed as darcies (1 darcy 0.987 10–8 cm2), millidarcies, or micrometers squared.
The capacity to flow fluids is one of the most important properties of reservoir rocks. As a result, extensive research has been applied to describe and understand the permeability of rocks to fluid flow. In this chapter, only single-phase or absolute permeability will be considered. Multiphase relative permeabilities must be derived using relations described in the chapter on relative permeability and capillary pressure. Permeability (k) is a rock property relating the flow per unit area to the hydraulic gradient by Darcy's law, ....................(14.1) The ratio q/A has the units of velocity and is sometimes referred to as the "Darcy velocity" to distinguish it from the localized velocity of flow within pore channels. The natural unit of k is length squared; however, petroleum usage casts Eq. 14.1 in mixed units, so that the unit of k is the darcy, which is defined as the permeability of a porous medium filled with a single-phase fluid of 1-cp viscosity flowing at a rate of 1 cm3/s per cross-sectional area of 1 cm2 under a gradient of 1 atm pressure per 1 cm.
The price of adding oil in shale plays will be rising this fall as the supply of wells that were drilled but uncompleted (DUCs) runs low. In the top five US shale plays, the total has dropped from more than 6,300 DUCs at the peak in the spring of 2020 to around 4,500 now, according to a report from Rystad Energy. That is the lowest since the fall of 2018 when oil prices were far lower than the current $70/bbl. Back then, the current price would have caused drilling to explode and production to rise, but not this year. Drilling is up this year from last year's deep slump, but it is just keeping up with the declines in older wells.
Oil and gas executives across the North American shale sector are continuing to come to the table and negotiate a steady stream of deals to consolidate portfolios. During the second quarter, the deal making amounted to more than $33 billion in mergers and acquisitions, according to data from Enverus. The energy-focused analytics firm said last month in its quarterly review the combined figure represents more than 40 deals, with seven of them topping $1 billion each. The third quarter has so far not seen any announced transactions surpass the $1-billion mark. Instead, most deals struck in July were between mid-sized and small US-based operators.
Relative permeability and capillary pressure defined capillary pressure as the difference in pressure across the interface between two phases. Similarly, it has been defined as the pressure differential between two immiscible fluid phases occupying the same pores caused by interfacial tension between the two phases that must be overcome to initiate flow. With Laplace's equation, the capillary pressure Pcow between adjacent oil and water phases can be related to the principal radii of curvature R1 and R2 of the shared interface and the interfacial tension σow for the oil/water interface: The relationship between capillary pressure and fluid saturation could be computed in principle, but this is rarely attempted except for very idealized models of porous media. Methods for measuring the relationship are discussed in Measurement of capillary pressure and relative permeability. Figure 1 shows a sketch of a typical capillary pressure relationship for gas invading a porous medium that is initially saturated with water; the gas/water capillary pressure is defined as Pcgw pg-pw.
Drought conditions rated as "moderate or worse" affected 31 US states as of 8 June, as reported by the US National Integrated Drought Information System. Particularly dry are the West and Upper Midwest regions, relevant to the Permian and Bakken, respectively. While not a record-level drought, attention is turning to the Missouri River in North Dakota where streamflow levels are at low levels for this time of year--about 48% below the seasonal average. In the extreme drought, water restrictions could come into play. Throughout the industry, recycling and reuse of frac and produced water have been studied, and where the chemical makeup of the frac or produced water is suitable for optimal and economical treatment, it has been implemented.
Recently, global climate change and air quality have become increasingly important environmental concerns. Consequently, there has been a rise in collaborative international efforts to reduce the concentration of greenhouse gases and criteria pollutants. Greenhouse gases include carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), occurring naturally and as the result of human activity. In addition, criteria pollutants (1970 amendments to the Clean Air Act required EPA to set National Ambient Air Quality Standards for certain pollutants known to be hazardous to human health) include emissions of nitrogen oxide, sulfur dioxide, carbon monoxide, and total unburned hydrocarbons. International and national governments are implementing more regulations on air emissions.
Equinor recently offered another possible future for engineers in oil and gas exploration and production (E&P) during the transition. By the end of the decade, the Norwegian energy company plans to be producing about as much oil as it did in 2020 but with a lot smaller global footprint. That is part of its plan to maximize its cash flow to support the growth of carbon-emission-lowering ventures, such as offshore wind power and long-term carbon storage. "Early on, oil and gas will mostly contribute to that return. As we move to 2030, it will be more and more renewables," Anders Opedal, Equinor's chief executive officer, said during the company's recent Capital Market Day with investor analysts.
Introduction Petroleum data analytics is a solid engineering application of data science in petroleum-engineering-related problems. The engineering application of data science is defined as the use of artificial intelligence and machine learning to model physical phenomena purely based on facts (e.g., field measurements and data). The main objective of this technology is the complete avoidance of assumptions, simplifications, preconceived notions, and biases. One of the major characteristics of petroleum data analytics is its incorporation of explainable artificial intelligence (XAI). While using actual field measurements as the main building blocks of modeling physical phenomena, petroleum data analytics incorporates several types of machine-learning algorithms, including artificial neural networks, fuzzy set theory, and evolutionary computing.
Yi, Ming (CNPC Xibu Drilling Engineering Company Ltd) | Liu, Ling (CNPC Xibu Drilling Engineering Company Ltd) | Wei, Qiang (CNPC Xibu Drilling Engineering Company Ltd) | Chen, Liang (CNPC Xibu Drilling Engineering Company Ltd) | Li, Binging (CNPC Xibu Drilling Engineering Company Ltd) | Guo, Zhiqi (CNPC Xibu Drilling Engineering Company Ltd) | Xu, Yangyang (CNPC Xibu Drilling Engineering Company Ltd) | Huang, Xingning (CNPC Xibu Drilling Engineering Company Ltd)
Abstract Exploration focus is moving into deeper targets of high pressure and high temperature (HPHT) regime due to the ever-increasing energy demand of China. Overpressure and wellbore instability related problems in such setting are mainly associated with narrow drilling margin resulting in severe well control incidents and increased drilling cost. In order to reduce drilling risks and operation costs, an accurate geomechanical model is necessary. The model provides technical support for drilling process and minimum reservoir damage due to optimal mud weight program. Well-scale (1D) Mechanical Earth Model (MEM) is constructed on the offset wells which consist of rock strength properties and stress profile by incorporating all available data including open hole log data, geomechanical core lab results, LOT/FIT, direct pore pressure measurements and drilling events. Furthermore, 3D geomechanics model is generated using available well-scale MEM data in the field and distributed throughout the field which guided by seismic interpretation data as distribution control. The 3D geomechanical model is used to design mud weight and casing program for the upcoming well. The offset wells in the study areas were drilled through complex geological settings with high overpressure (13500 psi) and high temperature (200-220 deg C). Therefore, drilling operations is also risky with different types of drilling events encountered frequently including stuck pipe, inflow, losses and connection gas etc. With 3D geomechanical model as the foundation, the integrated approach helps ultra-deep wells to reduce serious wellbore instability caused by abnormal formation pressure, wellbore collapse and other complex drilling problems. The implementation of systematic and holistic workflow has proven to be extremely successful in supporting the drilling of HPHT wells in China. The integrated solution has been applied in the ultra-deep well, recorded an improvement in ROP by 35.3% and decrease no-productive time (NPT) by 25.3% compared with offset well. The geomechanical approach provides a convenient means to assist field engineers in the optimization of mud weight, risk assessment, and evaluation of HPHT wells drilling performance. The findings will provide reference and guideline for de-risk and performance improvement in HPHT wells drilling.