Введение - Система сбора и подготовки скважинной продукции на месторождении Карачаганак

Kazakhstan is the second largest oil producer among former Soviet republics after Russia, with output of 693,000 bbl/d in 2000. Almost half of Kazakh oil production comes from three large onshore fields: Tengiz, Uzen, and Karachaganak. Kazakhstan has been eager to tap its production potential of over 3 million bbl/d, and former Prime Minister Nurlan Balgimbayev (now the head of Kazakhoil) has estimated that Kazakhstan could earn $700 billion in revenues (including taxes) from offshore oil and gas fields over the next 40 years.

Karachaganak is one of the world's largest oil and gas condensate fields. The expansion of the field has involved an investment of over US$4,3 billion and it is currently the biggest internationally funded project in Kazakhstan. The field development is being overseen by four international partners - British company BG Group and Eni of Italy, each with a 32,5 percent interest, Chevron of the USA with 20 percent, and LUKOIL of Russia with 15 percent. They came together to form Karachaganak Petroleum Operating BV (KPO).

While Karachaganak and KPO had their own share of controversy in the past, compared to the environmental difficulties of the Tengiz field operated by Chevron and the well-publicized troubles of Eni, the operator of the giant Kashagan field, the Karachaganak project can be regarded as a success story.

However, despite these successes (which certainly helped to keep off Kazakhstan's tax police and environmental authorities), Karachaganak faces many of the same problems that all oil and gas producers, especially foreign companies, are exposed to.

The main challenge is the geographic location of the field and the lack of distribution options for the natural gas extracted from the field. Due to the Russia-centric nature of the Soviet gas pipeline network, the only existing export option for Karachaganak gas is to Russia, more specifically the Orenburg Gas Processing Plant just across the border. Currently, KPO sells its gas to KazRosGas, a joint venture between Gazprom and KazMunaiGas, which in turn exports the gas to Orenburg and then to other CIS states through the Russian gas pipeline network. This arrangement leaves KPO in a vulnerable position because of the lack of any alternatives. Thus, KPO itself is unable to market its gas in Western Europe and is forced to sell its gas to KazRosGas at a significant discount to European market prices.

Another challenge is the structure of the field; like the majority of Kazakh gas fields, it is a gas condensate field. Due to the lack of viable export options for gas, the focus at the development of the field has been on liquid hydrocarbons (oil and condensate) which can be exported to Western markets via the CPC pipeline (all Karachaganak partners hold shares in the pipeline). For a long time, gas was seen as a semi-useless byproduct rather than a valuable export commodity like oil. One reason for this is the above described lack of export routes for the gas; another reason is the low quality and high sulfur content of the gas that requires further purification before it can meet contractual specifications as to export quality.

KPO has responded in slowing down the development of the natural gas portion of the field and has tried to find alternate uses for the natural gas it extracts.

First, it re-injects significant quantities of gas into the ground to maintain crude wellhead pressure for liquids extraction - at this point about 6 billion m3 of gas per year. Re-injected gas can then be recovered at a later date.

Second, it uses the extracted gas as power generator for its own facilities at Karachaganak.

Re-injection is used as a method of enhanced oil recovery to compensate for the natural decline of the field production by increasing the pressure in the reservoir, thus restoring the desired level of production and stimulating the recovery of additional crude.

Recycling of natural gas or other inert gases causes the pressure to rise in the well, thus causing more gas molecules to dissolve in the oil lowering its viscosity and thereby increasing the well's output.

Using this technique the field exploitation can be increased by up to 20%.

And preparation of the sour gas for re-injection, which is carried out on Karachaganak field, is considered to be an important part of the whole process.

The analysis of crude's gathering and treating system on Karachaganak field, which is the topic of this diploma work, covers the following items: inside trade gathering of well production; primary and secondary separation of condensate, oil, gas and water. The purpose of this work is to offer the possible way of solution to improve separation processes on the gas processing facility called Unit-2. It is conducted not only for sour gas preparation to re-inject it, but also for facilitating gascondensate's further preparation and treatment processes.

Unit 2 is where the gas compression and re-injection equipment is located.

The other main equipments at Unit 2 are slug catchers for oil and gas separation and glycol contactors for sour gas dehydration prior to re-injection. Liquids are sent to KPC for treatment.

The gas compressors are manufactured by Nuovo Pignone and at the limits of proven technology. There are three units operating in parallel configuration. Each unit has a capacity of 2.2 Billion cubic metres per year. The suction pressure is 70 bar and the discharge pressure is up to 550 bar. The compressors are three stage with interstage air-cooling.

As these facilities are dedicated to prepare sour gas for re-injection it is one of the ways to find alternate uses for the natural gas extracts, as it was mentioned earlier. And, from this point of view, the chosen theme can be considered as a vulnerable present-day topic in terms of not only Karachaganak's field development, but also for the whole Oil and Gas industry's development.

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Введение - Система сбора и подготовки скважинной продукции на месторождении Карачаганак

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