Research On Key Technologies For Gas Drilling In Daqing Oil Field

In recent years, the focus of the oil exploration has shifted from the middle/shallow layer to deep natural gas exploration. With the thorough development of oil and gas exploration, higher drilling technology is requested. In deep formations of Daqing oilfield, it has high geothermal gradient, high degree of hardness and abrasivity. Compared daqing deep well drilling technology with the international advanced level, there is great gap between them. In order to discover and protect reservoirs, improve penetration rate of drilling deep wells, Daqing oilfield has successively carried out researched on underbalanced drilling technology, combined drilling technology etc, although it had increased deep well drilling speed, they can not fully meet the requirements of the natural gas exploration of high temperature layer, compact rock formation and low permeability reservoirs. To realize exploration of deep natural gas, it need to largely enhance the drilling speed, shorten the drilling time, discover and protect reservoirs without delay and decrease the drilling cost. Gas drilling is a kind of underbalanced drilling, it can increase the drilling speed by 4-8 times and can be beneficial to discover and protect reservoirs timely and improve ROP, and it is of great significance especially for competent formation and compact reservoir. So the study and appliance on gas drilling is an ideal technology to speed up the pace of exploration of deep natural gas and increase exploration and development benefit.Gas drilling is a revolutionary technology and has been applied widely in domestic and abroad. On the basis of what has already been achieved in this field, this paper studied six key technologies such as the gas drilling parameter, deviation control, judgment method of formation water and blockage of water influx to wellbore etc, and formed a system theory and matching technology for gas drilling of Daqing oilfield. It is of great significance to expand the use of gas drilling, effectively reduce drilling cycle, reduce the drilling cost and raise the successful probability of exploration of Daqing oilfield. Through research and application, the paper gets some main conclusions as follows.1) By analyzing present situation on penetration rate of drilling deep wells in Daqing Oilfield and elaborating on the advantages of gas drilling, gas drilling has been the most effective method to improve drilling efficiency in deep formation. By using the method of minimum speed and minimum kinetic energy, a set of reasonable drilling parameters and full-size bottom hole assembly(BHA) are determined according to the comprehensive analyze about well structure, formation drill ability, hole stability and water exit.2) By a comparison with hole deviation of gas drilling and conventional drilling, influencing factors and the mechanism of well deviation in gas drilling are clarified. Owing to the existence of negative pressure, force conditions of the wellbole are changed. The force to break the rock decrease and fragmentation volume increase significantly. The bit drill along the craters, hole deviation is easy to take place. Gas drilling change the stress state of bottom hole rock, anisotropy index of formation is magnified, so that the formation natural deviation force increase. This is the root cause of well deviation and uncontrollable during gas drilling.3) On the basis of seepage mechanics, the computation formula of formation water yield and the solving method of differential pressure are presented. Through computing and analyzing, evaluation results of gas drilling adaptability in Daqing oilfield are provided. The results provide theoretical base for the further application of gas drilling in Daqing oilfield.4) This article firstly indicates the water shutoff method with bearing oppositely, and a series of laboratory experiments are performed. Physical simulation experiment show that acrylamide gel is adapt to gel packer formulation, oxides of Ammonium sulfate and Ferrous sulfate are adapt to gel breaker for the gel plug and slow releasing of capsules is used to break. As long as the fluid gel packer can meet the requirements, water yield formations can be blocked effectively during air drilling.