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Perforated completion is a main method of horizontal well completion. Based on the mass conservation equation, the momentum conservation equation and the variable mass flow in the horizontal wellbore, pressure drop calculation models of the wellbore fluid are established in perforated completion of horizontal wells. The results of calculation and analysis show that the frictional pressure drop, acceleration pressure drop and mixing pressure drop have different effects on total pressure drop of the wellbore fluid, and the frictional pressure drop plays a major role while the acceleration pressure drop and mixing pressure drop have little influence. The liquid viscosity, production and horizontal wellbore length also have different effects on various kinds of pressure drop. When liquid viscosity is smaller and the length of the horizontal wellbore is shorter, the effects of the acceleration pressure drop and mixing pressure drop cannot be neglected. The theoretical basis and the calculation model of the variable mass flow pressure drop of horizontal wellbore are provided.
Perforated completion is a main method of horizontal well completion. Based on the mass conservation equation, the momentum conservation equation and the variable mass flow in the horizontal wellbore, pressure drop calculation models of the wellbore fluid are established in perforated completion of horizontal wells. The results of calculation and analysis show that the frictional pressure drop, acceleration pressure drop and mixing pressure drop have different effects on total pressure drop of the wellbore fluid, and the frictional pressure drop plays a major role while the acceleration pressure drop and mixing pressure drop have little influence. The liquid viscosity, production and horizontal wellbore length also have different effects on various kinds of pressure drop. When liquid viscosity is smaller and the length of the horizontal wellbore is shorter, the effects of the acceleration pressure drop and mixing pressure drop cannot be neglected. The theoretical basis and the calculation model of the variable mass flow pressure drop of horizontal wellbore are provided.
The development of Oman gas accumulations requires the use of hydraulic fractures as part of the sand face completion, multi fractured horizontal wells were identified as potential well architecture that allow effective hydrocarbon recovery while reducing the number of well. The unique geological properties of the reservoirs require different fracture strategies and technology deployment to make them commercially viable. Fracturing High Pressure High Temperature (HPHT) as well as Multilayer Differential Depleted (MDD) formations takes the implementation of this technology to its limits; the challenges are further increased by stress regime variations due to tectonics and rock properties heterogeneities encounter across the horizontal section, challenging the effective placement of transverse fractures, fracture conductivity and final hydrocarbon gas deliverability. It is well agreed the multivariable nature of this challenges, however these are not well understood. A holistic approach was used starting with the fractured vertical wells in both challenging environments (HPHT & MDD) this providing the stepping stone for the definition of the fracture implementation strategies in horizontal wells. It was possible to identify three key areas influencing the fracture implementation, these covering design, monitoring and diagnostics; from this three areas, fracture diagnostics was a vital stage on fracturing optimization, on this stage the use of pressure and rate data, radioactive tracers, microsismic monitoring were used to provide information about fracture propagation behavior, geometry and containment; on the other hand, production logging and well test data were used to assess fracture conductivity and inflow performance. The combination of calibrated fracture and inflow simulation platforms were essential for the analysis of the considerable amount of data generated as part of the diagnostic stage. However, commercial available analytical and numerical inflow tools provide limited options to incorporate details variations of fracture conductivity, effective fracture length and inertial affects across the fracture plane. This paper will describe the developed methodology used for fracturing horizontal wells that combines extensive data acquisition and evaluation in combination with the development of in-house software platforms with commercially available tools and how it was incorporated the detail results from calibrated fracture simulation and characterization with inflow analytical and numerical models, this to estimate the inflow performance across the fractured interval and the subsequent generation of inflow profiles (Synthetic Production Logs). It will be also discussed the comparison of the estimated inflow profiles with measured inflow from production logging (PLT). Finally it will be presented how through the use of the developed methodology was possible to optimize completion, perforation, fracturing and production strategies critical aspects for field development.
In recent years, horizontal drilling has become increasingly important to the oil and gas industry to enable efficient access to complex structures and marginal fields and to increase the reservoir contact area. New technologies have emerged during this time to address post-drilling intervention challenges in such wells. However, complexity of operations in horizontal wells is much higher than that of the vertical wells; therefore effectiveness of the selected technique has a major impact on the operational success and economics. In depressed market environment, economical and operational effectiveness becomes even more important especially when it’s down to complicated, challenging projects that require not only large investments but also simultaneous and continuous utilization of multiple resources, technical disciplines and assets. This paper reviews and compares different ways of horizontal multizonal well preparation for hydraulic fracture stimulation using plug & perf technique in challenging downhole conditions - differential pressures over 15,000 psi, presence of depleted zones complicating cleanout and milling operations between the frac stages, depth control issues. In PDO, there are some gas fields sharing similar downhole conditions whereas fracturing operations are complicated by the requirement of CT cleanouts and/or milling in between the stages. A horizontal well development trial has been implemented to evaluate its economic efficiency and prospects. Depending on the success of this trial, this approach can be spread to other fields with similar characteristics. In these trial wells, multistage completion technologies were not available due to either differential pressure limitations, downhole conditions or completion restrictions, therefore conventional plug & perf approach had to be applied. Such approach, in turn, becomes very challenging in horizontal wells crossing several different formations having multiple severely depleted intervals along the wellbore. These challenges include not only cleanout efficiency and precise depth control during zonal isolation and perforation but also conveyance capabilities. Several different techniques have been tried in PDO so as to discover the most efficient and economical way to complete this task: CT with deployed wireline cable, CT with fiber optic cable, DH tractors and conventional CT with GR-CCl tools in memory mode. All of them have their pros and cons and while saving some money in one small thing, a technique may cause major losses in the other and an operator needs to select the optimum approach taking into consideration multiple aspects. All technologies covered in the paper are well known in the oil business; however some of them were tried in an uncommon environment. For example, although not commonly used in horizontal frac applications (except for perforating for the first stage), tractors were used for plug setting and perforating between the stages and that required well cleaned wellbore for each run which is not an easily achievable task in a horizontal wells with multiple depleted zones. With certain measures aimed to improve their performance, tractors proved their efficiency; these measures are also discussed in this paper. Advantages and disadvantages of CT conveyance in comparison to tractor have also been discussed. E-line tractor technology has been successfully deployed in the Sultanate of Oman for reservoir surveillance using production logging assemblies in mature fields. Tractors provide specific advantages, as compared to other forms of conveyance, such as coiled tubing, and can successfully negotiate complex well trajectories in both horizontal openhole and cased hole well completions, enabling acquisition of good quality flow profiles in producers and injectors.
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