Tailoring of the Fracturing Technologies to Challenging Geological Conditions of Jurassic Formation of Yamal Peninsula

Abstract Novoportovskoe field is one of the largest oil, gas and condensate fields on the Yamal Peninsula. The Jurassic reservoir is the main productive horizon at that field. It contains 50 % of oil reserves and it is described by a 45-meter deposit with a gas cap and bottom water. The main risk during hydraulic fracturing, in the absence of barriers, is the proximity of gas- and water-bearing formations. The hydraulic fracture breakthrough into gas and water zones leads to a significant decrease of oil production rate. The main objective of the described project was a selection of fracturing technologies, which would minimize the indicated risk. A number of technologies was introduced to control the vertical growth of the hydraulic fracture: polymer-free fracturing fluid to reduce the viscosity and enhance the hydraulic fracture cleaning. The technology of enzyme fluid breaker that enables to significantly improve the retained conductivity of the hydraulic fracture compared to standard oxidative breakers. The efficiency of enzyme breaker does not directly depend on the concentration but advantages of the enzyme breaker increase at low formation temperatures. The safe ball launcher allows minimizing the amount of fluid injected during hydraulic fracturing. A series of studies was conducted to analyze the hydraulic fracture geometry: Microseismic Monitoring at Multistage Hydraulic Fracturing; Long-Spaced Cross-Dipole Sonic Log, which allows determining the hydraulic fracture height. Production logging tests were performed to assess the productivity and identification of ports with a breakthrough into water- and gas-bearing horizons. The implementation of various technologies and methods of hydraulic fracturing ensured to significantly enhance the well productivity and influenced the field development plan. The obtaining of a low gas ratio and water encroachment percentage was a key criterion for success of the performed operations. As a result, in most of the wells, the gas ratio does not exceed 500m3/t and water encroachment is not more than 40%. Currently, the enzyme breaker and ball launcher are the preferred methods for multistage hydraulic fracturing in the Jurassic formations of Novoportovskoe field. The well treated with polymer-free fracturing fluid has one of the lowest gas ratio (387 m3/t) and oil production rate of 100 t/day. The ball launcher made it possible to reduce the volume of the injected fluid during hydraulic fracturing by 30% and to decrease the operation time from 5 days to less than 2 days. The approach developed and technologies selected showed a stable growth of productivity and complete applicability of hydraulic fracturing under Jurassic horizon conditions of this unique field. Stimulation operations under complicated geographic and geological conditions give some opportunities for the oil industry in the Arctic.