Известия Томского политехнического университета: Инжиниринг георесурсов (May 2018)
Laboratory studies of acid compositions for treating reservoir, characterized by various carbonate content and void structure of rocks
Abstract
The relevance of the research is caused by the fact that the productive carbonate deposits of oil fields of Perm Krai are characterized by a considerable variety of structural-genetic types of rocks and void specific structure. The exploration of deposits with void complex structure is accompanied by the difficulties in implementing a highly efficient water flooding system and, as a consequence, reducing reservoir pressure and well productivity. To increase wells productivity in carbonate reservoirs the acid treatment is carried out. The effectiveness of acidic exposure is advisable to perform taking into account the peculiarities of the void structure and the carbonation of the rocks being treated. The main aim of the study is to carry out the laboratory studies for assessing the effectiveness of acidic compounds in the oil fields of Perm Krai, characterized by different carbonate content and the structure of rocks void. The methods: a device for determining the carbonate content of rocks, carbonatomer KM-04M, filtration units with simulation of formation conditions of UIP-5VG and AFS-300 and microfocus fluoroscopy. The results. For each type of void the authors have simulated the acid effect using two common compositions applied in Perm Krai, determining a permeability change factor and with X-ray tomography studies. X-ray tomography experiments on a single core sample were performed twice: before and after modeling the acid effect. The acidic effect almost on all samples with an initially uniformly porous structure of the void, led to formation of a pronounced highly conducting filtration channel - the «wormhole». The filtration studies carried out on fractured samples of the Gagarinskoe field did not lead to any significant result: the acid compositions passed through the cracks without leading to an increase in either the total voidness or the permeability of the samples. It was determined that acid composition penetration into microfractures development zone can lead to a change in the acidic effect direction; acid composition injection into intervals with pronounced fracturing does not lead to high processing efficiency. It was determined that the void structure and the carbonate content of the rocks of the oil fields in Perm Krai are the factors that determine the effectiveness of the acid effect.
