Selection of Hydraulic Fracturing Candidates in Iranian Carbonate Oil Fields: A Local Computerised Screening of Zone and Well Data
Authors: Hashemi Abolfazl , Shadizadeh Seyed Reza , Zoveidavianpoor Mansoor 
Published: March 2015

Abstract
Hydraulic Fracturing (HF) is a mature technique to rehabilitate the productivity of a hydrocarbon formation, but Iranian oil companies are taking the primary steps to practice it in their oil fields. A couple of operations have been practiced but the unproductive results emphasized on the importance of Candidate Selection method. There is not a standard procedure or computerized tool to select primary candidates from Iranian carbonate oil fields. This paper presents the development of a locally written interface to automatically select specific zones for special operations like HF. The program is written in MATLAB in such a way to anticipate the missing data by Neural Network and Fuzzy Logic technique and then integrate large amount of data from different disciplines. In the end, data are mechanically screened based on the user selected parameters, cut-offs and weight factors. Results of screening within the limitations are prioritized in stacked bars to make decision easier. This tool is applied for a purpose of candidate selection for HF in M oil field located in south of Iran. This field has 585 zones which each zone has more than 30 parameters form different disciplines. The result of this programming is printed schematically and it is easy to see the quality of each criteria. This technique can be applied for unlimited number of zones and wells.

Introduction
Most of Iranian oil fields have passed their plateau production rate and about 200,000 bbl/d of crude production be lost annually due to natural pressure declines of the fields1. Moreover, with natural flow only 20% to 25% of the original oil in place is extracted from Iranian carbonate oil reservoirs, which is 10% less than the world average. Therefore, the new era to look for new technology just started to maintain and increase the production. Application of gas lifting system, electrical submersible pumps, sucker rod pumps and hydraulically fracturing the formation are being considered to maintain the well production rate. HF technology as introduced worldwide is an effective approach that can make the difference and can grant new life to old mature fields2. Various advantages make HF a superior type of production enhancement in carbonate reservoirs. This subject along with the needs for HF was addressed briefly by Zoveidavianpoor et al. (2010, 2011b)3, 4.
Although HF operation has more than 60 years of history and every day hundreds of treatment is performed around the globe, however, still there is not any report of successful HF operation in Iran. In order to have well-adapted HF technology, detailed geomechanical studies and well integrity test such as leak-off test, minifrac test, calibration test, etc., have to be performed. Unfortunately, those bottom-line studies are not implementing in Iran. Investigation of Shadizadeh and Zoveidavianpoor, 20105; Zoveidavianpoor et al. 2011a6., have shown that the lack of data/information about rock mechanical properties, regional in-situ stress, and specially no consideration of candidate selection study, were the main reasons of failure in HF operation.
The advantages of successful HF are so much that Iranian oil companies are trying to develop HF technologies in some oil fields. As clearly cited in the literatures, successful HF operation primarily depends on systematic candidate selection. The disappointment of a rare cases of HF in southern Iranian oilfields indicate that to accept HF technology as a replacement stimulation method and also, increasing the recovery factor, significant efforts have to be concentrated on zone and well candidate selection. As a result, a research project has been proposed and started in National Iranian South Oil Company (NISOC) to investigate candidate selection for HF in three oilfields named: "A", "M", and "AR".