Operational peculiarities of gas-condensate wells with flat ending in overpressure conditions and low reservoir properties (by the example of the Achimov deposits of the Urengoy oil and gas condensate field)

Today Achimov deposits of the Urengoy oil and gas-condensate field are the most complicated reservoirs for development in the north of West Siberia. Due the deficit of the actual data in the first engineering documents there were made a lot of calculations both with use of the analytical modeling and with use of the reservoir simulation modeling for justifying a way of pay zones penetration. The recommendations on pilot operation sincluded, but not limited to testing of drilling technology and operation of a well withsub-horizontal ending without fracturing. The results of assessment of the process efficiency of reserves recovery on the basis of the analysis of the process operational indicators over the long-term period and the results of systematic geological and field surveys for wells of this type of completion are presented in the paper.
Materials and methods
The surveys in the paper are based on the geological and field data on the development of the Achimov gas-condensate deposits of the Urengoy field. Based on the results of hydro-dynamic and gas-condensate surveys there are developed the analytical model sof gas-condensate mixture filtration to the bottomholes of sub-horizontal wells. As a result of simulation experiments with the analytical models of wells inflow of various constructs in Software Kappa Sapfir there were defined the areas of condensate dropout defining the productive characteristics.
Results
The advantage of a well with vertical penetration with fracturing versus a sub-horizontal penetration without fracturing is caused by creation at a relatively large distance from the well bottomhole a high conductivity channel with formation, which is definitely increases the drainage area and helps move across the zone of filtration resistances, detected in the wells with subhorizontal penetration and high permeability of afracture itself which is many folds more than the formation permeability, helps carrying over gas-condensate mixture even at a low differential pressure between bottomhole and fracture wings. So the detected skin-factor in wells with fracture is between -5.5 to -6.8 and remains the same eight years as a minimum, it is more preferable compared to sub-horizontal penetration as by the end of the first yearof operation there observed an increase of filtration resistances in BHZ and skin-factor tothe positive value.
Сonclusions
Thus as a result of the pilot operation of the Achimov deposits of the Urengoy oil and gas-condensate field with use of sub-horizontal penetration without fracturingit is obvious that it has a weak efficiency compared to vertical penetration and use of fracturing. Today the results of the analysis of the process indicators of operation and interpretation of geological and field surveys give evidence of the best process efficiency of the Achimov deposits of the Urengoy oil and gas-condensate field development in case of the use of a combination of two penetration ways - subhorizontal penetration with multi-stage fracturing which allow connecting several fractures together with one conductivity channel (well).