Research And Application Of Acid Pressure Technology In Dagang Buried Hill High Temperature Oil And Gas Reservoir

With the deepening of exploration and development, Dagang buried hill reservoir shows the huge development potential. Despite international oil prices keep falling recently, but the international oil price fluctuations is temporary, in the long run, buried hill unconventional resources development still be a direction for future development. So, continue to technical research, prepare technical reserves is necessary. Due to the feature of Dagang buried hill reservoir (deep reservoir; high temperature; high fracture pressure; low porosity; low permeability; thin reservoir; strong heterogeneity; micro-fissure is much; natural productivity is low; high requirements of acid system, string and technology), some achievements have been made,by the past acid fracturing, but in order to get a better development benefit, we must improve reservoir recognition. According to different formation conditions, select the corresponding acid system and acid fracturing technology, in order to achieve the needs of different reservoir. For this purpose, in this paper, we based on the depth acid fracturing theory, research summary, indoor experiment and field test, carried on the detailed study, carried out the following several aspects:(1) Fully understand tectonic and geological characteristics of Dagang buried hill reservoir:The overall composition is complicated, uneven distribution, big difference, contains gypsum and pyrite. When we choosing acid formula should be fully appreciated; there are two types of reservoir pore space in Dagang buried hill:porous-fractured medium and porous medium. Reservoir types distribution has the characteristics of sequence, ribbon, partition. The main layer temperature as high as 165??185?,fluid properties:lighter oil, heavier gas and saltier water.(2) Combining the condition and effect of acid fracturing technology in the past, comprehensive evaluation the adaptability of buried hill reservoir acid fracturing technology in Dagang oilfield. Most used gelling acid fluid closed acid fracturing technology, for low permeability, low fissure development, poor connectivity of stratum, unable to realize the deep penetrating acid fracturing, also unable to communicate far well zone by fissure. Due to the effect of complex tools and well conditions, packer multi-layer hierarchical acid fracturing has poor applicability. Single acid fracturing technology can't achieve the goal of deep measures.(3) Combined with the reservoir conditions, the acid-rock corrosion mechanism, crack extension mechanism and process adaptability, Summarizes selection principles of acid fracturing technology in Dagang buried hill:determine the front multi-stage alternating injection closed acid fracturing technology is the measure which can realize deep penetrating, long crack, high diversion, and applicable to Dagang buried hill reservoir.At the same time, we made selection principles of acid fracturing string and process parameter.(4) Determine the direction of the liquid system,by according to the geological characteristics:low filtration, high temperature resistant, low reaction rate, easy flow-back; selected four sets of deep penetrating acid fracturing fluid system:neutral cross-linked fluid and cross-linked acid, self-diverting acid, gelled acid. With their on-site experiments, measures achieve good results.