# Measuring Gas Flaring in Russia with Multispectral VIIRS Nightfire
## 1 Introduction
### Context of Gas Flaring in Russia: Regulations and Reported Data Availability  
According to the Russian Tax Code [27], only the gas that is extracted via oil wells is considered associated petroleum gas, or APG (P.II, Chapter 26, Article 337, s. 2, ss. 3: \"... Natural fuel gas (dissolved gas or a mixture of dissolved gas and gas cap gas) from all kinds of raw hydrocarbon deposits which is extracted via oil wells (hereinafter referred to as 'associated gas')?). APG has been the main focus of governmental regulations aiming at reducing gas flaring in Russia, with higher taxation multipliers applied to the over-limit emission fees. Government regulation, in effect since 2013, aims to achieve 95% APG utilization (i.e., 95% of extracted petroleum gas must not be flared or vented), while increasing fees for over-limit gas flaring [28] (Order, Item 3), with a 25\(\times\) emission fee multiplier applied to the fields with existing over-limit (i.e., \(>\)5%) flaring since 2014 (Provision, Item 2). However, there are several major cases in which this coefficient is not applied or is applied partially:  
* The over-limit fee is not implemented unless either three years have passed since the start of commercial exploitation of the field (since 1% of the oil reserves have been extracted) or more than 5% of the oil reserves have been extracted (Order, Item 3);
* An increase in flaring volumes at the oil fields induced by temporary maintenance at the related gas processing plants is excluded from gas utilization efficiency calculations (Provision, Item 4);
* Investments into APG utilization infrastructure can be used to (partially) cover the over-limit part of the fee (Provision, Item 7). According to the WWF Russia [29], near complete coverage of flaring facilities with flow meters measuring gas flow rate parameters inside the flaring stack was achieved in the mid-2010s. Still, it is reported that some companies may use other methods to assess flaring emissions even if the flow meter is installed, which may lead to biased interpretation of the data [30]. Together with potential errors in flow meter measurements in field conditions and uncontrolled flaring during maintenance procedures, this makes the reported data to some degree inaccurate, allowing companies to flare c. 20% of the over-limit APG, avoiding increased fees, while up to 30-40% of flaring is not taxed as it happens on greenfields, as cited in [30] (p. 236). Annual gas flaring data in Russia at the highest level of regional subdivision (federal districts) and the national level are publicly available in the Unified Interdepartmental Information and Statistical System (UIISS) maintained by Rosstat (Russian Federal State Statistics Service) [3]. Regional- and subsidiary-level gas flaring data are also provided by \"CDU TEK\" (subsidiary of Ministry of Energy) on a commercial basis, while the Ministry of Energy publishes annual national- and major company-level reported data on APG production and utilization rates [1; 2]. Subsidiary-level data by \"CDU TEK\" may in some cases correspond to single fields, thus partly yielding field-level data. In Khanty-Mansi Autonomous Okrug, Yugra, regional authorities (Department of Mineral Resources and Department of Supervision of Natural Resources) publish annual gas flaring data (quarterly data are available for 2012-2016 period) [31; 32]. Company-level data are also published by the major oil companies in their annual or sustainability reports, usually in the form of APG production and utilization rates on a company scale. Such a way of reporting leaves a possibility of error in interpretation while converting the APG extraction and APG utilization efficiency data into gas flaring volumes. In recent years (c. since 2015), Gazprom, Gazprom Neft, and Lukoil directly reported company-level gas flaring volumes, while Rosneft reported flaring volumes or APG utilization rates among its major subsidiaries. Comparison with these data is presented in Section 3.3.