The limestone water plugging technology
The limestone water plugging technology
Carbonate reservoir develops fracures and caves, the formation temperature of which is high (approximately 120℃).These reservoirs can be connected by Acid Fracturing and after a period of exploitation, the bottom water will be linked up resulting in rapid increase of the water cut furtherly causing the remaining oil hard to flow into the wellbore. Only to control the bottom water channel does we have the possibility of extracting remaining oil from distant well area. Consequensely, we decide to use chemical water plugging method which can form a control baffle to block bottom water run into the channel as to decrease water cut and stablize the oil production.
By injecting undispersed water shut agent into the production formation, taking advantage of diffrent density of agent, oil and water,we successfully make the liquid layered in the deep formation which followed shut-in coning control principle. The shut agent will solidate to clog the water coning channel decresing the production resistance to complish the goal to increase the production.
The shut-in method: Using undispersed shut-in agent to achieve cloging the deep area, taking advantage of diffrent density of agent,oil and water, and its undispersity, we successfully make the liquid solidated when meeting with the salt and layered in the deep formation which can curb the bottom water runing upstreamly to the production formation cloging the oil channel and achieve incresing production.
The steps as followed:
1 After remedial work, the water shut-in tubing was put in the well to measure the height of liquid column within the wellbore
2 Beening separately injected with two slug, the agent will privilegedly flow into the fracture with lower resistance
3 Make sure the production channel by injecting displacement fluid(water making) and remove the agent out of the production formation(relatively thin).
4 after the agent beening displaced out of the wellbore, as for the different density of formation water(1.13), agent(1.09),displacement liquid and formation oil(0.95-1.03), under the circumstance of the high temperature, the clog is formed under 5491－5528m in deep formation which achieve the goal of blocking the bottom water channelling.
5 Shut in the well and wait the agent to solidate(when the pressure of the wellhead down to zero, examine downhole liquid level depth as to inject the water in time preventing the agent Regurgitation ).change the production tubing and start to producting.
A field trial was conducted succcessfully in Tahe oil fleid, and achieved a good result. The technique has been experimented with 3 wells two of which proved to be positive, the cumulative increased oil 2300t.
The well TH10104 was implemented with the water shut-in technique in April,2010. After the implementation,oil production can reach 39t/day at peak, water cut down to 0﹪ at lowest。 With effective production time of 2 months, average oil production 20t/day, acumulative oil production of 1110t, oil incresing is evident.