Lost circulation plugging technology
Overview：
We have eight sets of plugging technologies, including rapid plugging technology, high fluid-loss solidification plugging technology, strong network plugging technology, high temperature resistance plugging technology, weak gel plugging technology, chemical gel plugging technology, reservoir fracture plugging technology and strong pressure-bearing plugging technology. The success rate of plugging at one time is more than 90%, providing technical support for solving the lost circulation problem.
Rapid Plugging Technology
概述：
PF-BLN 1/2/3/4 and PF-MOBLN 1/2/3/4 is the representative product.It is composed of nuts with different particle sizes, mica and vermiculite, which can be used for rapid sealing. It is suitable for all kinds of leakage in drilling fluids and has obvious plugging effect.
Applicability：
Loss control (loss rate > 5 m3/h)；Suitable for water, non-aqueous based drilling fluid；Applied in high permeability and fractured formation；Temperature:≤150℃
Characteristics：：
Sealing layer can be formed rapidly；High plugging efficiency；Good compatibility with drilling fluids；Inert material
High Fluid-loss Solidification Plugging Technology
概述：
PF-STP is the representative product.It is a kind of milky white fibrous mixture. It can bridge in the fracture, and form mud cake by high fluid-loss. Finally, solidify to improve the strength of the mud cake, so as to form the sealing layer.
Applicability：
Loss control (loss rate > 30 m3/h)；Cannot be used with bit and logging tools；Temperature：≤180℃；Reservoir plugging
Characteristics：：
Prepared from fresh water, sea water and salt water；Rapidly high fluid-loss；High-intensity plugging layer；High acid solubility
Strong Network Plugging Technology
概述：
NETLOCK is the representative product.Strong network plugging technology is an auxiliary series of products to improve plugging efficiency for serious lost circulation, with compressible and high resiliency network plugging structure. It has three different sizes. It needs to be used with other plugging agents at the same time. The product will form a perfect "filter net" after entering the fracture. It allows the fluid to pass through the itself easily. The NETLOCK will move slowly in the fracture, which is used to slow down the moving speed of the bridging particles. The captured bridging particles are then gathered together to form a whole plugging layer quickly, thus filling the fracture space effectively. This process can improve the success rate of plugging significantly.
Applicability：
Loss control (loss rate>10 m3/h)；Temperature: ≤140 ℃.
Characteristics：：
Compressible and highly resilient；Hollow porous；Reduction of the permeability of plugging layer；High success rate for plugging of loss circulation
High Temperature Resistance Plugging Technology
概述：
PF-BLN HT is the representative product. High temperature resistance plugging technology is composed of high temperature resistance rigid particles, mica and mineral fiber with planned particle size distribution, which can be used for plugging rapidly in drilling process. It is suitable for all kinds of losses and has effective plugging act.
Applicability：
Loss control (loss rate > 30 m3/h)；High permeability and fractured formation； Water-based drilling fluid systems；Temperature: 150~220 ℃.
Characteristics：：
Sealing layer can be formed rapidly, with obvious plugging effect;High temperature resistance.
Weak gel plugging technology
概述：
PF-VEL is the representative product. It is a series of auxiliary leakage stoppage products for serious lost circulation, generally used with rapid plugging technology. It has good shear dilution, high static shear force and elastic modulus increasing with time. In order to make it flow, it must overcome static shear force and elastic resistance. After entering a certain depth of the leakage layer, the plugging agent can automatically stop flowing and fill the fracture and cave , forming a "gel slug" that can separate the internal fluid of the formation from the wellbore fluid, so as to improve the success rate of plugging.
Applicability：
Loss control (loss rate > 30 m3/h)；Temperature：≤160℃
Characteristics：：
Good shear dilution；Effectively retard the lost circulation rate；Significantly improve the success rate of plugging
Chemical Gel Plugging Technology
概述：
PF-CHEMGEL is the representative product.Chemical gel plugging technology is a temperature sensitive, underground crosslinked reinforcement chemical gel. It is a new chemical gel plugging agent. After the liquid is pumped into the formation, the gel will be crosslinked with the crosslinking agent under the influence of temperature, forming a strong elastic three-dimensional gel structure. It can be used for the control of losses through large fracture or cave leakage during drilling operations.
Applicability：
Loss control (loss rate＞30 m3/h)；Applicable temperature: ≤180℃
Characteristics：：
Nontoxic and environmentally friendly；Controllable cross-linking time；Excellent elasticity once being cross-linked
Reservoir Fracture Plugging Technology
概述：
PF-FRACSEAL F/M/C is the representative product.Reservoir fracture plugging technology is composed of acid-soluble rigid particles with proper size distribution, flake materials, and acid-soluble fibers. Particles and flake materials can bridge in the fracture. The fibers are reinforced. The small particles can then fill in the fracture space. Finally a dense temporary plugging layer is formed, which can effectively plug the fracture and improve the formation pressure bearing capacity. The acid solubility of this plugging material is greater than 90%.
Applicability：
Loss control (loss rate >10 m3/h)；Applicable temperature: ≤220℃
Characteristics：：
Sealing layer can be formed rapidly, with obvious plugging effect;Acid soluble, easy to remove plugging.
Strong Pressure-Bearing Plugging Technology
概述：
The main function of strong pressure-bearing plugging technology is to improve the pressure bearing capacity of weak or fractured formations. By optimizing the particle size distribution, shape, type and proportion of different materials, this technology can achieve broad-spectrum plugging of different fractures. The sealing layer’s strength and efficiency is much better than the traditional plugging technology. This technology saves drilling time and cost.
Applicability：
Weak and fractured formations；Temperature: ≤200 ℃
Characteristics：：
Wedge plugging，High pressure bearing capacity；Good suspension stability.
Rapid Plugging Technology
(1) Challenges
The 8-1/2 "borehole of a Bohai CFD well was drilled to 3780m with a drilling displacement of 1800L/min, the first leakage occurred, and the drilling fluid density was 1.34g/cm ³； Instantaneous leakage speed 34m ³/ h. Reduce the discharge to 600L/min, and the leakage rate is 18m ³/ h； Static without leakage.
(2) Resolution
① Forced drilling while drilling, add PF-SEAL, PF-SZDL, PF-BLN 1 to the circulating pool, and the leakage rate is reduced to 5m ³/ Within h.
② Drilling to 3941m, displacement 1500L/min, leakage rate increased to 18m ³/ h. Reduce the discharge to 1000L/min, and the leakage rate is 3~4m ³/ h. The low displacement does not meet the orientation requirements, and the bridge blocking operation shall be carried out in a short time. POOH to the pipe shoe, RIH to 3900m, throw ball to open the bypass valve of the plugging nipple, and replace 17.5m of the plugging slurry ³ (Full open hole coverage), plugging slurry formula: well slurry+5% PF-SZDL+8% PF-SEAL+10% PF-BLN 1+5% PF-BLN 2, cement pump squeeze plugging slurry 9.5m ³， The pump pressure is stabilized to 3.96MPa, and the calculated bottom hole equivalent density is 1.45g/cm ³， There is no leakage in circulation.
③ Continue drilling to 3950m and increase the leakage rate to 20m ³/ h. Displacement: 1600 ~ 1700l / min, gel front-end + bridge plugging, displacement: 9.5m ³ Gel and 17m ³ Plugging slurry (full open hole coverage), plugging slurry formula: well slurry+5% PF-SZDL+8% PF-SEAL+10% PF-BLN 1+5% PF-BLN 2, cementing pump squeezed 2.5m into the plugging slurry ³。 The pump pressure is stabilized to 7.8MPa, and the calculated bottom hole equivalent density is 1.55g/cm ³， There is no leakage in circulation.
④ Continue drilling to the completion depth of 4322m. After the completion of electrical logging operation, leakage occurred during the well trip. In order to meet the pressure bearing requirements of cementing after plugging, replace the bare drill pipe for pressure bearing operation, upgrade the bridge plugging slurry formula, and replace the plugging slurry for 36m ³ (covering 200m above the pipe shoe), 10% PF-SEAL+10% PF-BLN 1+10% PF-BLN 2+10% PF-BLN 3+5% STP. The extrusion pressure is stabilized to 5.57Mpa, and the calculated equivalent density is 1.48g/cm ³， A total of 1.1m of plugging slurry is squeezed in ³， Meet the cementing requirements, and the cementing operation is smooth without leakage.
(3) Plugging effect
① Forced drilling while drilling, with leakage rate controlled at 5m ³/ Within h.
② The second time of leakage, the cement pump is used to squeeze and inject 9.5m of plugging slurry ³， The pump pressure is stabilized to 3.96MPa, and the calculated bottom hole equivalent density is 1.45g/cm ³， There is no leakage in circulation.
③ The third time of leakage, the cementing pump is squeezed 2.5m into the plugging slurry ³。 The pump pressure is stabilized to 7.8MPa, and the calculated bottom hole equivalent density is 1.55g/cm ³， There is no leakage in circulation.
④ For pressure bearing operation, the squeezing pressure is stabilized to 5.57MPa, and the calculated equivalent density is 1.48g/cm ³， A total of 1.1m of plugging slurry is squeezed in ³， Meet the cementing requirements, and the cementing operation is smooth without leakage.
