Factor Analysis of Basic Production
Authors: Oleynikov Vitaliy , Cherkovskiy Nikolay 
Published: October 2019

Abstract
A brownfield basic production generally provides at least 90% of total production, it is sometimes called current declining well stock production or even free one. It is on the brownfields where accurate understanding and operational control of basic production are especially important.
The most important and complicated features of the basic production are related to its all-time decrease, that can be traced to such things as watercut increase during the stock work out, well stock disposal and others, impact of which is difficult to calculate in the obvious way.
An existing process of direct change of basic production calculation by types and factors is presented in this article.
Tasks to be solved are limited by the determination of wells, causes and magnitudes of changes in basic production with the reason of making operational decisions on the application of operations, as well as by the generation of statistical data with the reason of the basic production dynamics prediction.
The first key step is to select the well stock, the main basic production (wells without the previous year GTO) and unsteady basic production (the GTO wells of the previous year).
Differentiation of the main and unsteady basic production allows to consider the volume of previous year GTO and to increase the accuracy of the projection.
The second step is the calculation of daily average oil production reduction factors: the changes by debit, by the operational efficiency and by the average well stock.
Factor clarification identifies the production decline reasons and allows to select effective corrective operations.
The algorithm automation allows conducting of an analysis of the history and obtaining of reliable statistical base for risks calculating of basic production eventually. The basic production forecast calculating is made according to the analysis factors, it allows to control the deviations causes of the actual forecast performance.
The main result of the work is the development and continuous use of factor analysis of basic production, determination of production change by factors for each well, formation of targeted corrective operations, risk assessment for basic production on a one-year planning horizon.
The developed complexes and combinations of calculations, conditions and filters made it possible to form a unique algorithm for the direct calculation of all the factors affecting on basic production "without a trace".
The developed visualization tools allow working with large data arrays and easy integrating of the results at the required level (cluster wells sites, development objects, oilfields, workshops).
For the first time a methodology for the risks assessing of basic production based on historical data was developed and used with the ability to clarify the impact of any period.
Selected activities show the high efficiency.
The approach development is determined in the way of automation and expansion of the causes determining functional of changes in the basic production, in the improvement of visualization tools.
A method of basic production decline target rate calculating based on the factor analysis of basic production is now being developed for operating programs developing to minimize the basic production decline rate.
This work is an important step in the development of basic production management efficiency based on objective operational monitoring of well operating modes.