Abstract

Production of residual reserves (1–1.5 billion m3) under low formation pressures in West Siberia as well as withdrawal of a strained gas from watered areas is always a trouble. Traditional methods used today to develop such fields are characterized by low hydrocarbons (including stained gas) extraction efficiency and production cost rise that even affects the reliability of a gas producing company operating performance.

Herein, results of theoretical researches and laboratory tests on the displacement of natural gas through the injection of nitrogen into the formation are presented.

Qualitative and quantitative data demonstrating the in-situ injection of nitrogen at the Medvezhye field are also shown.

Introduction

At the final stage of gas field production there is a time when the pressure of residual gas in the productive layer is about 5 MPa, not more. In the case of bottom water intrusion the rate of pressure reduction slows down, that compensates partly the negative subsequences of the water drive process. So, some or less significant zones of the residual gas resources could be trapped behind the gas-water front. But, in many cases the share of trapped gas and low pressure gas could be such significant (tens of percents from the gas-saturated portion of reservoir), that it is necessary to apply some additional arrangements for those losses reduction. According to VNIIGAZ estimation, the residual low-pressure gas resources at the biggest gas fields in Western Siberia (Medveje, Urengoy, Yamburg) in the case of those fields just depletion will exceed 1.5 billion m 3 and trapped gas makes the most part of those losses – 75%.

One of the way to increase the gas fields development efficiency is the reduction of hydrocarbons losses including those from trapped and low pressure gas in the productive layer. This is important task both from scientific and practical point of view.

The results of seam inundation process investigations at the conditions of noncompensible hydrocarbons production, made in VNIIGAZ, evidence that even in homogeneous porous medium trapped gas is distributed not uniformly. For example, the data obtained with topographical methods, evidence that at Medveje field, where the average gas saturation is about 15–20%, there are zones where the real gas saturation is much more and could exceed the hydrodynamic mobility edge.

These data obtained stimulate further investigations for the method development, which could provide the residual trapped gas resources involvement into their active production.

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IFINAL STAGE OF NATURAL GAS FIELD DEVELOPMENT

We had the intentions to develop the method, which is not based at the both big bulk of associated water and gas itself production (the correspondent information could be tak

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