An unconventional evaluation of the Kazhdumi Formation in two northwest fields of the Persian Gulf

The Persian Gulf, as the richest hydrocarbon pool in the world, plays a very important role in the world's energy equations. Approximately two-thirds of proven oil reserves and one third of global natural gas reserves are available to the Persian Gulf States. Iran's water borders in the Persian Gulf hold a significant portion, 16 oil fields developed in Jurassic, Cretaceous and Tertiary carbonate reservoirs.

 In this study, Rock-eval analysis was used and a series of calculations were performed for evaluating unconventional Kazhdumi source rocks in the A and C fields in the north west of Persian Gulf. According to the research and exploitation of hydrocarbon reservoirs in the world, today these reserves are divided into two main groups of conventional reservoirs and unconventional reservoirs. Conventional tanks are located in the form of oil traps, source rocks, reservoir rocks and rock covers. However, in unconventional reservoirs, with the presence of special petrological features, the possibility of direct exploitation of the source rock is provided. It is also possible that part of an oil system will be operated as a conventional reservoir and another part as an unconventional reservoir. In unconventional reservoirs, with mature source rocks converting organic matter to hydrocarbons, if permeability is created, we will be able to extract hydrocarbons. This is done at the shale gases, that are currently being used around the world.Gas shales are a diverse group of rocks in which methane is trapped. Then methane is extracted from gaseous shale by distillation or hydraulic fracturing. Today, oil and gas shales are a good alternative to conventional hydrocarbon resources due to depletion of conventional ones.

 Gas shales have a high content of organic matter. If organic matter enters the gas window maturely and the dry gas production stage is ongoing, then on-site gas generation takes place in them. This is considered as shale gas (unconventional tanks). For this purpose, by drawing geochemical logs of parameters S1, S2, S1 + S2 and TOC (Table 1), field data A and C were examined. There is evidence of good to very good hydrocarbon generation power at the source rock. Then, by examining the characteristics of Barnett shale (as a producer and important shale in the United States) the set of geochemical parameters of the Kazhdumi Formation for A and C fields have been compared with the minimum threshold values in Barnett's shale.

Kazhdumi Formation has a small amount of gas production in field A, and is located in the C field between oil and gas windows. The evaluation of the vitrinite reflection coefficient, the maturity of the samples and the probability of the gas shale potential are investigated. The results of the TR-RO graph have represented the biogenic source of gas production in A and C fields. In deeper depth, there is a higher production of gas for this formation in the A and C fields.