Multilateral drilling (ML) drilling technology is one of the unconventional drilling methods to increase the productivity of a well. It is thought that ML wells could be more economic with higher productivities than other types of wells such as vertical, directional, horizontal or extended reach horizontal wells. Advances in ML drilling has resulted in significant cost saving, greater flexibility and increased profit potential. In the last two decades, thousands of ML wells have been drilled worldwide. Around 10 percent of the total wells are ML. During 1980s, advances in horizontal technology were adopted quickly in the Middle East to bring about dramatic improvements in well productivity. Many operators in the Persian Gulf region looked at ML drilling technology as a next step from horizontal drilling technology. These operators started to drill ML wells after experiencing successful drilling of horizontal wells. Since the early 1990, the use of ML drilling technology in the Middle East has seen significant growth to the extent that Middle East is one of the most active areas in the world for ML applications. This paper investigates the benefits of ML drilling as one of the highly expanded methods. Advantages and challenges of the ML technology are highlighted. Since Middle East is one of the most active areas in the world for ML applications, therefore, two case studies from this region are reviewed. The first case study is the first Saudi Aramco's deep ML gas well, and the second is drilling a dual lateral well in Dukhan field in Qatar. For the former case study, productivity of ML wells is presented. Furthermore, a comparison is made between the productivity of a horizontal and dual ML in order to give a recommendation for one of them. Introduction Unconventional drilling is a growing part of the global drilling activity. In the past several years directional, horizontal, extended reach horizontal and multilateral (ML) wells have been drilled successfully using unconventional drilling techniques. Unconventional drilling technologies play a key role today where conventional technologies are not fully efficient to keep development profitable. These technologies allow us to increase production per well but also to improve ultimate reservoir recovery factor (RF). ML drilling as one of unconventional drilling techniques emerged at the beginning of nineties.1 The general definition of a ML well is one in which there is more than one horizontal or near horizontal lateral well drilled from a single side (mother bore) and connected back to a single bore. 2 During 1980s, advances in horizontal technology were adopted quickly in the Middle East to bring about dramatic improvements in well productivity. Many operators in the Persian Gulf region looked at ML drilling technology as a next step from horizontal drilling technology. These operators started to drill ML wells after experiencing successful drilling of horizontal wells. Since 1992, the use of ML drilling technology in the Middle East has seen significant growth to the extent that Middle East is one of the most active areas in the world for ML applications. 3 In 1996, it is estimated that over 35 MLs were drilled in the Middle East. 4 Among the Middle East countries, some invested more on of ML technology are Saudi Arabia, UAE, Oman, and Qatar. Examples of leading companies in the region in ML technology are Saudi Aramco and ZADCO. Other countries in the region are progressing in application of ML technology. An overview to applicability of ML technology in the Middle East countries has been done by Mirzaei Paiaman and Moghadasi (2009).5
The modeling and simulation of commingled production from multilayered shale-gas reservoirs is presented and the changing pressures and flow rates in various zones are simulated. An effective iterative numerical simulation is developed for the coupled wellbore and reservoir hydraulics calculations for multi-layered shale gas reservoirs. The performance of each layer communucating with the wellbore, in the absence or presence of formation cross flow, is evaluated and demonstrated by case studies. Changes in the permeability of shale with prevailing conditions is accounted for by considering the apparent gas permeability in shale depending on the pore proximity effects. This rigorous simulation method presented here enables an accurate evaluation of the pressure and production at each layer including the cross flow effects.
In Drilling Oil Wells a system of complex fluids and chemical additives is used. Losses of these fluids in the well during drilling or disposal of them in well site could transfer pollutants to groundwater. In the present study a number of well sites, located in South of Iran, were studied to indicate types and magnitude of various pollutant materials that remain in the environment undestroyed and have considerable impacts on the underground water resources. Hydrocarbons used in Oil Base Muds (OBM) that can't be biodegrade readily in nature found to be the most severe pollutant material caused by disposal of Drilling Mud and Cuttings. Volume of drilling waste for these oil wells evaluated to be an average almost 0.5 m3 per one meter of drilled oil well. Available common treatment methods were compared to assess the most economically and environmentally attractive treatment scenarios. Thermal desorption and reserve pit without treatment are two most dominant methods could be conducted in Southern Oil Fields of Iran, each has its advantages and disadvantages. Due to geological structure and near surface aquifer in Khuzestan province thermal desorption should be conducted to disposal cuttings to reduce their hydrocarbon content to less than 5% according to European Standard. Major challenges of drilling waste management program in onshore oil fields of Iran were studied and clear principals for managing waste streams, which include: reduce, replace, reuse, recycle, recover, treat and final dispose, were listed along with material, equipment and strategies that should be considered in each step. Introduction Oil well drilling operations are responsible for the disposal of large quantities of drill cuttings and fluids. On a site of oil drilling, mud provide several important functions, lubrication of drilling bits, the maintenance of subsurface pressures, and transport of cuttings towards surface. It is a complex system of fluids based on water (WBM) or on oil (OBM), with several chemical and mineral additives. The formulation of these muds is adjusted with precision according to the physicochemical conditions of drilling, which change with the depth, and the nature of the crossed geological formations [3]. Other than the fluid (either water or oil or both) and the solid phases, different types of chemicals and polymers are used in designing a drilling mud to meet some functional requirements such as appropriate mud rheology, density, mud activity, fluid loss control property etc. Though the factors that guide the choice of a fluid base and the mud additives are complex, the selection of the additives must take account of both the technical and environmental factors to eliminate any environmental impact [4]. Due to potential detrimental effect of non-environment friendly drilling fluids, Environmental Protection Agency (EPA) and other regulatory bodies are imposing increasingly stringent regulations on the use and disposal of non-environment friendly drilling fluids, whether it is water-based or oil-based [4].
Rock mechanics is the theoretical and applied science of the mechanical behavior of rock, the branch of mechanics concerned with the response of rock to the force fields of its physical environment. In hydraulic fracturing, rock mechanics is important in the determination of mechanical properties and the in-situ stress state of reservoir rock, the calculation of deformation and failure behavior of the rock mass caused by the treatment, and the determination of the fracture's final geometry Knowledge of mechanical properties variation is of great importance for Petroleum Engneering .mechanical properties is often measured in the laboratory from cores. Lab measurements is expensive and time consuming .Many correlations and models were used have been proposed to estimate mechanical properties using some lab measurements data. Different artifacial intelegence techniques were implemented in several studies. This work describes the use of Alternating Conditional Expectation Algorithm technique to estimate Poisson's Ratio and Young's Modulus as a function of Depth with lab porosity Overburden Stresses Pore Pressure ,Minimum Horizontal Stress measurements and Bulk Density (RHOB),DT Compressional and DT Shear from logs data In this study, 602 data points of lab measurements and log data were used The proposed models evolved estimates Poisson's Ratio and Young's Modulus with good accuracy with correlation coefficient ( R 2 ) of 0.994 and 0.974
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