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Zhang P.,Sichuan RenZhi Oilfield Service Co.
Drilling Fluid and Completion Fluid | Year: 2010

The success rate of controlling lost circulation may be low if the particle size distribution, concentration and volume of LCM mud pumped are only decided by the loss rate. A progressive method can be used in curing lost circulation; using fine particles at low concentration to medium or coarse particles at moderate or high concentration, and pumping while mixing the LCM mud. If the width or length of fractures taken mud is not quite defined, this method may provide a way of stopping lost circulation. This method has been applied in 6 wells for 7 times, and is 100% successful.

Zhang P.,Sichuan RenZhi Oilfield Service Co. | Wang H.,Sichuan RenZhi Oilfield Service Co.
Drilling Fluid and Completion Fluid | Year: 2010

Formation pressure distribution in west Sichuan is very complicated. When lost circulation is encountered, the well is often shut-in and LCM mud is squeezed to stop mud losses. When the well is then opened, the squeezed LCM mud flows back into the well. This phenomenon is also encountered during the switch of pumping, and is misleading since engineers do not know if there is a high pressure, or a low pressure encountered downhole. It is concluded, by comprehensive analyses, that this phenomenon results from the open and closing of enclosed fractures with pressures trapped in them. Some suggestions for prevention and treatment of this phenomenon are given in this paper.

Yu Z.,Sichuan RenZhi Oilfield Service Co. | Lv B.,Sichuan RenZhi Oilfield Service Co. | Yang F.,Sichuan RenZhi Oilfield Service Co. | Li B.,Sichuan RenZhi Oilfield Service Co.
Drilling Fluid and Completion Fluid | Year: 2012

Shale-related borehole instability is encountered in drilling operation in Chuanxi block, many layers of hardfriable shale are found in one open hole section. The mechanism of deep formation caving in Chuanxi block is studied and a dilute silicate anti-caving drilling fluid system is developed to replace the polysulfonate drilling fluid. The experimental results show that the density of that covers from 1.40 g/cm 3 to 2.20 g/cm 3. The application of this drilling fluid system in well ZX31 shows that the borehole enlargement rate is 6.43% in the third interval.

Zhang J.,Sichuan RenZhi Oilfield Service Co. | Deng M.,Sichuan RenZhi Oilfield Service Co. | Xie Y.,Sichuan RenZhi Oilfield Service Co. | Liang Y.,Sichuan RenZhi Oilfield Service Co. | Duan C.,Sichuan RenZhi Oilfield Service Co.
Drilling Fluid and Completion Fluid | Year: 2010

Well Hebal-1D, located in northeast Sichuan, is a high angle development well, having a maximum well angle of 66° and a completion depth of 5, 810 m. Highly deviated wells drilled in carbonate rocks in this area would face downhole troubles such as high formation pressure, high angle, high sulfide content, and coexistence of blowout and lost circulation. The fourth interval of the well Hebal-1D experienced 4 times of lost circulation of different severity. Two times of lost return were cured and technical casing strings were successfully cemented in place. Using hesitation shut-in (for 10 h) technology and strengthening the weak formations with LCM, hole interval with coexistence of high pressure and low pressure was successfully drilled and cemented. Coexistent blowout and lost return are finally prevented. The technology for lost return and high pressure control in deep, high pressure and high angle well used in this area provides a solution for the same technical puzzle in other area.

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