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Integrated approach to the exploration wells design for improving the exploration efficiency

UDK: 622.692.4
DOI: 10.24887/0028-2448-2022-1-40-44
Key words: oil, gas, hydrocarbons, Vietnam, offshore, drilling, testing, logging while drilling (LWD), pressure testing while drilling (PTWD), drill stem test (DST), mini-DST, multivariate well design, increase in efficiency
Authors: D.I. Varlamov (Research and Engineering Institute, Vietsovpetro JV, the Socialist Republic Vietnam, Vung Tau), V.V. Kotok (Research and Engineering Institute, Vietsovpetro JV, the Socialist Republic Vietnam, Vung Tau), A.A. Sadovnikov (Research and Engineering Institute, Vietsovpetro JV, the Socialist Republic Vietnam, Vung Tau)

The article discusses the applying of an integrated approach to the planning and detailed design of the exploration well, including identifying goals and objectives, developing a decision tree, justifying the use of modern research methods and technologies. This approach was used to obtain the maximum possible volume of reliable geological and geophysical information and increasing the efficiency of geological exploration at a complex geological object. At the preparation stage for the well drilling a multivariate design was implemented along with the optimal well head positioning for hydrocarbon bearing reservoirs exploration within several geological structures as well as decreasing of geological risks. The following technical and technological solutions were implemented during the drilling: geomechanics modelling and support, logging (LWD) and reservoir pressure testing (PTWD) while drilling, as well as testing in an open hole (mini-DST). It should be noted that PTWD and mini-DST technologies were used in Vietsovpetro JV for the very first time. Geomechanics service allowed to optimize the drilling mud parameters, to avoid complications during drilling and minimize the negative impact on the reservoir, as well as maintain the stability of the open hole 2 km long throughout the research. Geological and geophysical information (LWD and PTWD) obtained in real time allowed to perform an operational correlation, select coring intervals, evaluate reservoir properties and identify objects for mini-DST tests. As a result, due to the whole range of implemented technical and technological solutions, it was possible to avoid technical issues both during well drilling and long-term testing in the open hole, to obtain reliable characteristics of key objects, minimize all types of risks and significantly reduce the well cost. After the well completion hydrocarbon reserves and resources of Thien Nga – Hai Au field were estimated. Hydrocarbon production area of the key object (layer CS2 in Oligocene, the boundary of category 2P) increased by 25%, gas reserves (category 2P) increased by 70%, oil reserves (Miocene) (category 2C) – increased by 305%. The unit cost of the increase in hydrocarbon reserves due to drilling of the well 12/11-TN-4X was $10.87/TOE or $1.45/bbl. At the same time the cost of the increase in hydrocarbon reserves of the Thien Nga – Hai Au field is 2.3 USD/bbl (since 2012), which is the lowest value compared to other Vietsovpetro JV projects located outside the Block 09-1 area.


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