Petroleum Engineering College

Qingdao, China

Petroleum Engineering College

Qingdao, China
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Hou Z.,Petroleum Engineering College | Yan T.,Petroleum Engineering College | Sun S.,Petroleum Engineering College | Yuan Y.,The Experimental Group Of No1 Production Plant | Liu J.,Petrochina
Journal of Engineering Science and Technology Review | Year: 2017

Currently, unbalanced drilling technique is widely applied in the exploration and development process of acid oil and gas reservoir. However, the acid natural gas that invades under high-temperature and high-pressure conditions can easily result in underground failures, such as well kick and blowout. Thus, a calculation model for the multiphase flow of a wellbore that is invaded by acid natural gas was established in this study based on the principle and method of gas-liquid two-phase flow to reveal the multiphase flow regularity inside a wellbore after the invasion of acid natural gas, considering the phase change and solubility of acid gas under high temperature and high pressure. Meanwhile, a solution for the model was provided. Finally, in the case of the H75-29-9 gas well conditions in Jilin Oilfield, China, the change rule of physical properties and the change features of parameters, such as mud pit increment and pressure drop in the bottom hole after acid natural gas (methane and hydrogen sulfide) penetrated the wellbore, were obtained through an analog calculation. Results indicate that the H2S solubility inside the wellbore is greater than the CH4 solubility. Moreover, H2S is 135 times more soluble than CH4 in the bottom hole. The density of acid natural gas mutates near the wellhead. High H2S content implies that the mutation location is near the wellhead. The density mutation location of pure H2S mutates 400 m away from the wellhead, whereas the density of a 50% H2S mutates 900 m away from the wellhead. Within the same overflow period, a high H2S content implies a small pressure drop value in the bottom hole, mud pit increment, and shut-in casing pressure, and small volume fractions of gaseous phases at the wellhead and in the center of the wellbore. Backpressure and the gas-invaded quantity at the wellhead have great influences on pressure in the bottom hole, that is, a great backpressure at the wellhead implies a low pressure drop in the bottom hole. Moreover, less gasinvaded flow quantity implies a small pressure drop in the bottom hole. This study provides a theoretical basis for wellbore pressure control and well-killing construction under complicated conditions. © 2017 Eastern Macedonia and Thrace Institute of Technology.


Pei H.-H.,Petroleum Engineering College | Zhang G.-C.,Petroleum Engineering College | Ge J.-J.,Petroleum Engineering College | Liu X.-L.,Petroleum Engineering College | And 3 more authors.
Oilfield Chemistry | Year: 2010

Aimed at high salinity formation water and high bottom temperature in Tahe oilfield, an bis-quaternary ammonium salt surfactant DFA-12 was synthesized as viscosity reducer by the reaction of tertiary amine (RN (CH3) 2) and ethylene dibromide (Br (CH2)2).The optimal synthesis conditions were obtained as follows, the molar ratio of RN(CH3)2 to Br(CH3)2 was 2.602: 1,the reaction temperature was 90% and the reaction time was 24 h, and the purity of objective product reached to 98.53%. The results of emulsification experiments of the system obtained by mixing the super heavy crude oil (SHCO) from Tahe oilfield with the emulsifier solutions at mass ratio of 7:3,showed that DFA-12 had stronger salt tolerance than the other surfactants,which could still emulsify the SHCO in the brine of 214739.9 mg/L By Compound DFA-12 wi • th other surfactants, and the optimal formulation of the emulsifying viscosity reducer for the SHCO was determined; 0.25%DFA-12 +0.25% HES (amphoteric surfactant) +0.1% DFP (polymer). The viscosity of the SHCO is determined at 90% and the viscosity reducing rate is calculated on the basis of the viscosity of the SHCO, being of more than 98%.

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