Abstract

The paper deals with geological and development features of marine deep gascondensate fields in the South Caspian Basin. The Bulla-deniz Field is taken as an example. Specific features of the above field are as follows: its complicated geological structure; steep angles of formation dip (12°-22°); large height of the reservoir (about 1.500 m); large occurrence depth of producting horizons (5,500 m - 6,500 m); non-uniform structure of producing horizons; abnormal initial formation pressure (71.4 MPa); rather low formation temperature (110°C); abnormal pore pressure in clays; high clayiness of reservoir-rocks (up to 30%); inner water drive and deformation of reservoir-rocks in the process of development; dissipated hydrocarbon fluid in the pore space of reservoirrocks; high condensate content (412 g/m3); oil slugs. In addition, the initial phase state of the formation system was in keeping with the conditions below critical pressure and temperature, and therefore since the very beginning of reservoir exploitation the system had a two-phase state.

The Institute of Deep Oil and Gas Deposits, Azerbaijan Academy of Sciences, has carried out works concerning estimation of reserves, planning and analysis of the above field development.

Thus, a complicated geological structure of the field and also troubles while drilling resulted in the creation of methods for interpretation of geological-geophysical data to provide a reliable hydrocarbon reserves estimation and to choose effective systems of development.

The hydrodynamic calculation methods to calculate technological indices of the above type gascondensate fields development at various drives have been worked out.

To enhance the output of producing wells a new approach and calculation algorithm of condensate recovery with «dry» hydrocarbon gas out of a near-bottomhole area have been developed. Calculations and experimental tests performed have proved a high efficiency of the method suggested.

Introduction

Large gas-oil-condensate fields have been discovered and are now developed in the Azerbaijan sector of the Caspian Sea shelf. These fields have some specific geological features and vary in hydrocarbon distribution within formations.

Basic text

1. One of such fields is Bulla-deniz, located 55 km to the south from Baku, in the oil-gas rich area of Baku archipelago. Over 45 local rises have been identified in this region. They have been united into anticlinal zones originating onshore. This field is unique in some characteristic points described in this paper.

It should be noted that all design documents required for development of Bulla-deniz field were prepared in the Institute of Deep Oil-Gas Deposits of the Azerbaijan Academy of Sciences. With this purpose specialists of the Institute carried out detailed analysis, processing and interpretation of all available information for this field, studied geological-geophysical data and information on development of neighbor fields. This allowed to solve many problems regarding Bulla-deniz and similar structures. 1.1 Characteristic feature of tectonic structure of Bulla-deniz structure and folding systems in this area is occurrence of large longitudinal fractures near the axes acting as shields. Numerous fractures could be traced along the length of anticlinal folds.

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