Impact of Conventional Practices on Economic Efficiency as Illustrated by the Construction of Horizontal Sections of Multilateral ERD Wells and Fishbone Wells in Western Siberia
Authors: Frolov Maxim Pavlovich , Voitenko Dmitry Nikolaevich , Proshin Alexander Olegovich , Ivanova Anastasiya Andreevna , Shepelev Vitaly Igorevich , Verevochkin Alexander Alexandrovich , Pustovarov Viacheslav Alexandrovich , Ignatyev Sergey Vladimirovich 
Published: October 2021

Abstract
This paper is a detailed description of the first experience of an ERD wells horizontal section using ultra-low-viscosity drilling fluid as a drilling fluid implemented in the Russia land. This work has great value as an experience that allows to reevaluate the traditional views on the sole influence of drilling fluid parameters on the process of drilling wells.
The thesis considers the key aspects and practices of improving the technical and economy values of drilling the multilateral ERD wells and FishBone wells in Western Siberia by applying an integrated approach based on three key factors:
understanding the features of the rheology of drilling fluids; thorough analysis of the results of modeling wellbore washing and cleaning and comparing the calculated values with the actual values of the determined technological parameters in order to predict and control ECD; the collaborative work of the customer and the contractor, so-called "active supervising" methodology, aimed on making timely decisions for adjusting of the target requirements during the wells construction, "in situ" method, in order to achieve the made goals.
The main conclusions have been made during the work:
Effective and sufficient cleaning of annular space can be achieved with minimum values of drilling fluid rheology characteristics. Cuttings and marble bridging agent participate in the filter cake creation. The absence of marble bridging agent particles in the mud composition cannot be a reason of complications (absorption, sticking) when drilling low-permeability reservoirs. The concentration of the marble bridging agent should be determined, taking into account several factors: solids control equipment efficiency, formation permeability, density and drilling fluid composition. the recommended values for the parameters such as lubricant concentration and MBT, must be selected, firstly, based on comprehensive understanding of the idea of each parameter, and secondly, adequately assessing their significance under specific drilling conditions. Competent active supervising of drilling fluid has huge impact on the economy efficiency of well construction, whereas this approach can be beneficial for both the customer and the drilling fluid contractor.
The implemented on the project approach allowed to save up to 60% for the cost of 1m3 of drilling fluid for horizontal section, as well as to reduce the time spent on the wells construction. The main result of the work: two multilateral wells were successfully drilled with the DDI of 7.2 and 6.55 and high risks of lost circulation. Wells construction was completed by running the liner to the target bottom without any signs of landings. However, the most important achievement is the emerging prospect of replicating the proposed approach to drilling ERD wells for deeper deposits development, that allows us to expect comparable technical and economy effects considering drilling conditions.