ANALYSIS OF THE EFFECTIVENESS OF APPLYING HORIZONTAL WELLS FOR THE DEVELOPMENT OF RESERVES OF A GAS CONDENSATE FIELD WITH LOW FILTRATION AND CAPACITANCE PROPERTIES

Abstract

Link for citation: Tomskiy K.O., Nikitin E.D., Ivanova M.S. Analysis of the effectiveness of applying horizontal wells for the development of reserves of a gas condensate field with low filtration and capacitance properties. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 172-181. In Rus. The relevance of the study is caused by the complications that arise during the development of gas condensate fields for depletion with difficult thermobaric conditions associated with precipitation of a large amount of retrograde gas condensate in the pore space of the reservoir, and especially near production wells due to a drop in reservoir pressure, which ultimately can reduce productivity of wells twice of more times. At present, due to the development of technologies, the construction of horizontal wells has become a traditional method of increasing gas and condensate recovery, in which, by increasing the effective area of well drainage, drawdown values are significantly reduced at the same gas withdrawals or higher in comparison with vertical ones, which should also reduce the negative «condensate bank» effect with a cost-effective ratio of gas recovery factor to condensate recovery factor. In this regard, the issue of studying the effectiveness of applying the technology of horizontal wells in «complex» fields with an initial formation pressure close to or equal to the pressure of the onset of condensation with a high degree of heterogeneity, low reservoir properties and low thickness becomes relevant. The main aim of the research is to evaluate the technologies for the operation of gas condensate fields by vertical and horizontal wells under various technological modes of operation of wells for the final gas and condensate recovery, as well as to study the nature of condensate precipitation in the pore space in the conditions of an oil and gas condensate field with low reservoir properties. Object. The BU81-2 formation is characterized by a high content of heavy hydrocarbons in the composition of the formation gas, which begin to fall out immediately after the start of the operation of the object. The reservoir has a total thickness of 22 to 57 m, and the volume of gas-saturated rocks is 5463585 thousand m3, and the initial dry gas reserves are 130064 million m3. Methods: geological and hydrodynamic modeling on the software product T-Navigator (Rock Flow Dynamics). Results. It was found that a horizontal well with a perforated horizontal section of 1400 m is capable of producing as much gas as three vertical wells at multiple lower drawdown values, however, due to a larger drainage contour, condensate falls over a larger volume of the reservoir with a saturation below «critical» and therefore all the precipitated condensate becomes immobile, preventing gas from seeping to the bottom of the well and reducing the overall gas recovery factor/condensate recovery factor. It was also found that vertical wells under these initial conditions provide greater condensate production compared to horizontal wells, and more condensate is produced with a decrease in drawdown.