Influence of Abandonment Pressure on Recoverable Reserves, Special Application to the Depleted Dnipro-Donetsk Basin Reservoirs

Volumetric gas reservoirs are driven by the compressibility of gas and a formation rock, and the ultimate recovery factor is independent of the production rate but depends on the reservoir pressure. The gas saturation in the volumetric reservoir is constant, and the gas volume is reduced causing pressure drop in the reservoir. Due to this reason, it is crucial to minimize the abandonment pressure to the lowest possible level. Concerning Dnipro-Donetsk Basin (DDB) gas reservoirs, it is widespread to recover sometimes more than 90% of the OGIP. Often, OGIP was estimated not considering lower permeability gas layers due to inaccurate logging equipment used in the past, causing that such layers were not included in the total netpay. This is one of the reasons for OGIP overestimation and higher recovery factors. On many P/Z graphs, we observe that at certain drawdown, lower permeability reservoirs kick in lifting up P/Z plot curve. Abandonment pressure is a major factor in determining recovery efficiency. Permeability and skin are usually the most critical factors in determining the magnitude of the abandonment pressure. Reservoirs with low permeability will have higher abandonment pressures than reservoirs with high permeability. A specific minimum flow rate must be sustained to keep the well unloading process, and a higher permeability will permit this minimum flow rate at lower reservoir pressure. Abandonment pressure will depend on wellhead pressure, friction and hydrostatic pressures in the system, pressure drop in reservoir, and pressure drop due to skin. This last factor is often neglected, which sometimes leads to a significant reduction of the recovery factor. It is common practice that skin factor and pressure drop due to the skin are solved with well stimulation. Also, well stimulation has its limits concerning the level of reservoir pressure. It is very common that the stimulation effect of low reservoir pressure well is negligible or even negative. This is caused by the minimum required drawdown to flow back a stimulating aqueous fluid out of the reservoir. The required minimum drawdown is caused by the Phase Trapping Coefficient (PTC), which drives reservoir stimulation fluid cleaning behavior. For water drive gas reservoirs, Cole (1969) suggests that the recovery is substantially less than recovery from bounded gas reservoirs. As a rule of thumb, recovery from a water-drive reservoir will be approximately 50 to 75% of the initial gas in place. The structural location of producing wells and the degree of water coning are essential considerations in determining ultimate recovery. In the cases studied in this paper, we consider gas and rock expansion reservoir energy, if abandonment pressure needs to be coupled with a water drive, then it is recommended to use a numerical, not analytical approach.

Psychology of Terrorism: Intimidation by Destroying One’s Own Life in the Donetsk Basin

The article presents the psychological genesis of terrorism in eastern Ukraine, referred to as the Donetsk Basin, during the Soviet era, which resulted from prioritising coal over the lives of Ukrainians affected by famine, executions, evictions and repression imposed by Russians. The replacement of the ethnic composition of the population by people from Russia led to the formation of a group of colonisers of Ukraine. This required creating an atmosphere of constant tension, fear and criminalised violence. As a consequence, the Donetsk Basin has become a favourable environment for Russians and their supporters, who were potentially prone to terrorist acts, and the most dangerous category of such persons — suicide bombers. The paper describes the emergence of a wave theory concerning terrorism in Europe, radical movements in Ireland, Macedonia, Serbia, Italy and Spain, as well as the current state of terrorism in Italy, Germany, Japan and many other countries. It covers the first terrorist act of Russia’s hybrid war against Ukraine near the village of Kamyanka, in the Donetsk region, where a checkpoint of the Armed Forces of Ukraine was attacked by a suicide bomber using a minibus loaded with explosives. It was also a place where other similar terrorist acts took place and the manifesto of Australian terrorist Brenton Tarrant was distributed in the centre of Ukraine by a terrorist group from the Russian Federation in order to involve prone persons in subversive activities on racial and religious grounds. The study was created using a nonparametric typology, based on the analysis of at least two parameters: the nuclei of vulnerabilities (targets of influence) and the features of intrapsychic formations arising under their influence. This allowed identifying five psychotypes of potential suicide bombers: of a person who has lost emotional connection with the outside world; of a fanatic of faith, associated with the activation of ‘mortido’ — the desire for death; of a fanatic of an idea, which considers the cessation of life as a spiritual transformation, and martyrdom as an integral element of the spiritual path; of a potential suicide bomber associated with extreme manifestations of protest behaviour; persons with psychopathic changes in personality structure. The paper establishes the prevalence of these psychotypes and comparative possibilities of influencing each of them.