Loss return drop-out cross linked gel plugging process

Abstract

The invention discloses a loss-return leakage loss cross-linked gel plugging process, relating to the field of oil drilling. Pre-cross-linked gel plugging slurry is prepared in a slurry compounding tank and consists of water, a gel gelling agent, a gel strength conditioning agent and a bridge plug plugging propping agent, wherein, the gel gelling agent accounts for 0.8 to 1 percent of the total weight, the gel strength conditioning agent accounts for 3 to 4 percent of the total weight, the bridge plug plugging propping agent accounts for 5 to 7 percent of the total weight, and the rest is water. After all the components are dissolved and mixed fully, an optical drill rod is put into the position of 5 to 10m below a loss zone, the pre-cross-linked gel plugging slurry and a gel cross linkerare respectively and simultaneously injected to the loss zone in a well with the volume ratio thereof of 2.5 to 3.5 : 100. By chemical crosslinking and coagulation accelerating, the whole structural strength of the gel can be improved truly, and the one-time plugging success ratio is improved to be more than 50 percent.

Description

technical field [0001] The invention relates to the technical field of petroleum drilling, in particular to a cross-linked gel plugging process, and the invention is applicable to the repeated lost-return leakage in the Luohe Formation in the Longdong block. Background technique [0002] The buried depth of the Jurassic Luohe Formation in the Longdong area of ​​Changqing Xifeng Oilfield is about 700m-1200m, and fractures are well developed in some areas, especially vertical fractures. In the process of drilling, lost circulation occurs frequently. Aiming at the current leakage characteristics of the Luohe Formation in the Longdong area, combined with rich plugging experience, a complete set of "ZND-2 intelligent gel plugging agent, CDL-1 conventional gel plugging agent" has been successfully explored in the existing technology. Conventional gel leakage prevention and plugging technologies, such as glue bridge plugging agent and GD-I high-viscosity elastic plugging agent, ha...

AI Technical Summary

Problems solved by technology

However, the one-time plugging success rate of the conventional gel plugging process only reaches 41.54%. The main factors leading to the low plugging success rate are as follows:

[0003] ①Most of the Luohe formation in the Longdong area is a large-pore high-permeability low-pressure water layer, and with the intensification of formation water exploitation in the Longdong area, there are abnormal pressure zones in the Luohe formation in some areas of the block, and the formation pressure coefficient is only 0.75 Between -0.85, it is difficult to improve the pressure bearing capacity of the formation at one time by using conventional plugging technology, resulting in multiple leakage and repeated plugging

[0005] ③ The internal structure of several gel plugging systems currently used is loose and lacks uniform structural integrity, resulting in a serious shortage of compressive strength of the material itself, and no cementation with the leakage layer. With the erosion of the mud, it is easy to lose along the leakage Channel loss, resulting in a low plugging success rate

[0006] ④Once the conventional gel is formed, the viscosity of the system will not change. Even if there is a small amount of proppant, its overall compressive strength is basically constant and will not change with time. The strength growth in the middle and later stages of the formation is extremely limited; During the drilling process, the drilling fluid is repeatedly washed out, and the probability of lost circulation increases, which greatly reduces the plugging time

Images