Jin Shubo, Jin A, Li Binwen
(Northwestern Petroleum Bureau Planning and Design Institute, Urumqi 830011)
Abstract: Deep well horizontal well drilling fluid technology is a comprehensive technology , mainly considering wellbore stabilization technology, wellbore purification technology, high temperature stabilization technology, and lubrication and anti-seizing technology. Horizontal wells drilled in Tahe Oilfield mainly use MMH polysulfonate-mixed oil and composite metal ion polysulfonate-mixed oil drilling fluid systems. The author mainly introduces the field application technology, maintenance and use effects of the two systems.
Keywords: Drilling fluid, wellbore purification, wellbore stabilization and lubrication, protection of reservoir temporary plugging technology
1 Overview
With the development of Tahe Oilfield exploration and development Continuously deepening, in order to improve the development well network and increase oil and gas production capacity, seven horizontal wells were deployed in Tahe No. 1 and No. 2 oil fields. The oil field is located in the Shaya uplift of the Tarim Basin. The oil and gas layers are deeply buried. The wells drilled are all about 4,500m deep, and the geological conditions are complex. The upper Tertiary Kuqa Formation, Kangcun Formation and Jidike Formation sandstone and mudstone are unequally thick and weakly cemented, with poor diagenesis and good drillability. The sandstone has high permeability and the mudstone is mainly illite and has strong hydration and dispersion. ; The main component of the lower Jurassic and Triassic mudstones is mainly illite (36% to 60%), containing 15% ordered mixed layers (22% S) illite/montmorillonite, and individual sections contain 15% % disordered mixed layer (50% S) illite/montmorillonite. Mudstone is generally not easy to disperse when exposed to water, but there are: ① Hard and brittle mud shale bedding and micro-cracks are developed, and at the same time there are mudstones that are easy to hydrate and expand and disperse, which generates high expansion pressure, causing the well wall to peel off and collapse; ② Abnormal pores in the mudstone High collapse pressure caused by pressure and strong in-situ stress can easily cause mechanical instability. The liquid column pressure is lower than the mudstone formation pressure, the hydration of the same formation varies greatly, the mudstone formation pressure coefficient is higher than the oil layer, and the well wall stress is unbalanced and other geological factors. .
The upper formation can easily cause thick sand and mud cakes and sticky drill cuttings thick mud cakes to shrink and block. The drilling fluid must have strong coating, strong inhibition ability, good wall-building properties and lubrication. sex. The lower stratum has been severely denuded and collapsed, the well wall has become unstable, the well diameter has expanded, and the well is in an inclined and horizontal section. Drilling fluid must have effective anti-collapse measures. At the same time, due to the special characteristics of deep horizontal wells, such as high bottom hole temperature, complex lithology of the strata encountered when drilling, and deep deflection points and horizontal sections, it is necessary to prevent stuck, collapse, The requirements for well logging and cementing are high, and factors such as large amounts of drilling fluid make maintenance adjustments difficult and there are many engineering accidents.
2 Drilling fluid technical requirements
During horizontal well drilling, the main problems include the overall inclination of the drill string toward the lower well wall in the inclined well section, the sinking eccentricity, and the contact area between the drill string and the well wall. increases, resulting in an increase in the downhole friction coefficient. It is difficult to carry rock: the sliding direction of drilling cuttings changes from the axial sliding of vertical wells to the radial sliding of inclined well sections and horizontal sections. The drilling fluid uses axial lifting force to overcome the radial sliding force of drilling cuttings. It is difficult for the chip axis to slide downward. Generally, a sedimentary layer is inevitably formed in the inclined well section, and the thickness of the sedimentary layer increases with the increase of the well inclination angle. The deposition of drill cuttings to the lower well wall causes the uniformity of drilling fluid suspension to be destroyed, which is not conducive to the carrying of drill cuttings and increases the frictional resistance between the drill string and the well wall. In strata with developed bedding, poorly cemented sandstone, conglomerate layers and complex strata are prone to collapse and block loss. In severe cases, the drilling tool will be buried and the drill will become stuck. To sum up, the drilling fluid is required to have extremely strong lubricity, rock-carrying ability, anti-collapse ability and well wall stability. The wells in this area are relatively deep, so the drilling fluid is required to have good temperature resistance. Drilling fluids in the horizontal section need to consider reservoir protection.
3 Drilling fluid design
3.1 Wellbore purification technology
By improving the plastic viscosity, dynamic shear force, dynamic-to-plastic ratio and static shear force of the drilling fluid, etc. , with a high dynamic-to-plastic ratio, shear force, etc., the drilling fluid has good suspension carrying capacity, reduces the settling speed of drilling cuttings, and brings them out in time. MMH positive electrostatic glue and composite metal ion polymer (PMHC) were selected to adjust the rheological properties of the drilling fluid to ensure an appropriate annular flow rate, which can not only protect the well wall but also bring out cuttings. Foreign studies have pointed out that when the annulus inclination ranges from 0° to 90°, the higher the drilling fluid flow rate, the higher the annular purification rate. In horizontal wells, insist on regularly rotating drill tools and short trips. Rotary drilling tools are conducive to the removal of cuttings. First, the cuttings deposited on the lower well wall are pushed into the flowing drilling fluid and taken out of the wellbore by the drilling fluid flow; second, large pieces of cuttings are accumulated and ground into small particles. It is conducive to the suspension of rock cuttings and taking them out of the wellbore.
Controlling the wellbore trajectory can reduce flow resistance, reduce kinetic energy consumption, and facilitate the removal of cuttings. In addition, selecting appropriate annular return velocity and drilling fluid rheological parameters based on the wellbore structure and drilling tool assembly can not only ensure the carrying of drill cuttings, but also reduce the erosion and damage to unstable well walls.
3.2 Wellbore stabilization technology
In view of the issues such as mineral composition, physical and chemical properties and wellbore instability of Jurassic and Triassic mud shale, first of all, the drilling fluid must have Low filtration loss and good mud cake quality can effectively seal the bedding micro-fractured mud shale in a short time; secondly, it must have sufficient inhibition to effectively prevent the well wall from absorbing water and swelling, Collapse, while preventing the dispersion of drill cuttings and reducing the solid content; furthermore, controlling the appropriate annular flow rate of drilling fluid to reduce the erosion of the well wall by the drilling fluid. To this end, efficient anti-collapse inhibitors and polysulfonate-mixed drilling fluid systems were selected, and reasonable anti-collapse technical measures were adopted to meet the requirements of deep well horizontal well drilling construction. Use asphalt products FT-1, SMP, SPNH, NH4PAN and other sealing and anti-collapse treatment agents to mechanically seal bedding and cracks, increase the wall-building and sealing ability of drilling fluid, reduce water loss and mud cake permeability, and prevent drilling A large amount of liquid filtrate enters the formation. The strong oil adsorption characteristics of SN-1 solid emulsifier are used to participate in the formation of mud cake and form a hydrophobic oil film on the well wall, which can effectively control the invasion of filtrate and reduce the hydration of mudstone. Long-chain, high-molecular polymers have extremely strong ionic groups, polar groups and non-polar groups, which adsorb, bridge and flocculate with the clay surface, coating the mudstone and inhibiting the dispersion of the clay. At the same time, the anti-collapse and water loss reduction agent PA-1 is applied to improve the chemical inhibition ability of the drilling fluid, inhibit the hydration and dispersion of mud shale to the maximum extent, and prevent well wall collapse. PA-1 is a graft polymer of KHm and cationic components. K+ and cations work synergistically to improve the anti-collapse effect. The addition of cations improves the adsorption and hydration capabilities.
3.3 Lubricating and anti-seizing technology
Based on the specific drilling construction conditions of Tahe Oilfield and referring to relevant domestic and foreign technical data, after comprehensive analysis and research, the method of mixing crude oil was selected to improve the drilling fluid quality. lubrication performance. At the same time, SN-1 solid emulsifier is preferred as the emulsifier. In its molecular structure, it has cationic groups with strong lipophilicity and anionic groups with good hydrophilicity, which has an amphiphilic effect. After adding SN-1 to the mixed oil drilling fluid, the oil can be fully adsorbed, and the oil can be enriched by SN-1 to participate in the formation of mud cake. An oil film composed of emulsion droplets is formed on the surface of the mud cake, and the drilling tool The friction with the mud cake or well wall is transformed into the friction between the drilling tool and the oil film, which can greatly reduce friction resistance and torque. Through indoor experiments, the reasonable addition amounts of crude oil and SN-1 solid emulsifier were optimized to be 8% to 10% and 0.3% to 0.5% respectively. The recommended on-site addition amount of crude oil is 10% to 12%. In addition, in order to improve the lubricity of drilling fluid, under special circumstances, 2% to 3% solid lubricant plastic balls are added and half-buried in the mud cake to form a micro-support between the mud cake and the drilling tool or casing. It acts as a "micro-bearing" to avoid pressure differential stuck and reduce torque and frictional resistance.
3.4 Oil and gas layer protection
According to the research and analysis results of reservoir characteristics and damage mechanism, that is, the reservoir is non-weakly water-sensitive, and solid particle intrusion contamination is a major problem in drilling and completion. In order to adapt to the characteristics of the formation encountered during drilling and the special requirements of deep and horizontal well construction, and to simplify the construction process, water-based drilling completion was optimized from the aspects of economy, operability and protection of oil and gas layers. Well fluid system, and the implementation of shielding and temporary plugging technology to protect oil and gas layers, to maintain low solid phase, low filter loss, good mud cake quality as much as possible, and control the PH value at around 9 to match the reservoir. The drilling and completion fluid adopts the technical measures of direct conversion of shielding and temporary plugging technology on the basis of the upper composite metal ion polysulfonate oil-mixed drilling fluid, that is, the use of MMH positive electrostatic glue polysulfonate oil-mixed temporary plugging and composite metal ion polysulfide oil-mixed oil Temporarily plug the drilling and completion fluid system.
In addition to the above-mentioned factors, drilling fluid design must also consider the vertical well section, especially the long open hole section of the second and third open well sections, large sections of mudstone and interbedded mudstone and sandstone. Mudstone sections are prone to mud encrustation, and sandstone sections with thick mud cakes can easily cause obstruction. Drilling fluids must maintain low solid phase, strong inhibition, thin and tough mud cakes, and excellent lubricity to ensure safe and rapid drilling.
The first and second drillings mainly use potassium-based polymer drilling fluid system and positive electrostatic gel drilling fluid system. The third drilling adopts positive electrostatic gel polymer mixed oil temporary plugging drilling fluid system and composite metal ion polysulfonate oil mixed temporary plugging drilling fluid system. Each system is transformed in turn. Both the composite metal ion polymer non-dispersed system and the positive electrostatic gel drilling fluid system have strong suppression and low solid phase characteristics, and are suitable for rapid drilling in the middle and upper formations; the positive electrostatic gel polymer mixed oil temporary plugging drilling fluid system and the polysulfonate system have It has the characteristics of high temperature resistance, low water loss under high temperature and high pressure, and good wall-building ability. It is suitable for drilling in the lower well section; it is also suitable for drilling in oil and gas layers.
Composite metal ion polysulfonate mixed drilling fluid system formula: (40～50)kg/m3 clay + (2～3)kg/m3 soda ash + (3～4)kg/m3NaOH+ (2 ~5)kg/m380A51+2kg/m3PMHC+20 kg/m3SMP-1 (powder)+30kg/m3 sulfonated asphalt+(80~100)kg/m3 crude oil+2 kg/m3SN-1 (or SP-80)+…
Positive gel polymer drilling fluid system formula: (40～50)kg/m3 clay + (2～3)kg/m3 soda ash + (5～10)kgMMH + (5～10)kg /m3PAM+(2～4)kg/m3PAC-HV+(20～30)kg/m3SMP-1 (powder)+(20～30)kg/m3 sulfonated asphalt+(20～30)kg/m3SN-1+(80 ~100)kg/m3 crude oil +….
4 Brief overview of the drilling project
After running Φ244.5mm technical casing, the 215.9mm drill bit was used for directional deflection drilling of the seven horizontal wells drilled. The construction project is basically The data is shown in Table 1 below.
Table 1 Basic data of Horizontal well drilling in Tahe oil field
Continued table
5 Field application of drilling fluid Technology
5.1 Well wall stabilization technology
During the drilling process, the anti-collapse measures for the mudstone well section are: mechanically, in order to increase the pressure of the drilling fluid column on the well wall. Support, making it greater than the collapse density of the formation. The usage density of drilling fluid is 1.20~1.22g/cm3, which is 0.02~0.05g/cm3 higher than the normal usage density of the same layer of vertical wells that have been drilled in the area, and with the unique characteristics of drilling fluid The rheological characteristics reduce the erosion of the well wall and the pressure excitement caused by tripping and starting the pump. Chemically, we mainly supplement MMH positive glue, PA1, WFT-666, FT-1, SPNH, SMP-1, PMHC, and NH4-PAN glue to improve the quality of the mud cake and increase the inhibition and sealing effect of the drilling fluid on the formation. Plugging and collapse prevention capabilities; at the same time, the SN-1 solid emulsifier is used to adsorb crude oil to form an oil film on the well wall to improve the stability of the wellbore; in addition, it can also reduce the filter loss, so that the API water loss is less than 4ml. HTHP loses 9-10ml of water, thereby reducing the immersion depth of the well wall and laying the foundation for long-term safe construction.
5.2 Lubrication technology
The lubrication performance of drilling fluid is mainly crude oil. When the inclination angle of the well reaches 30° and when it enters the horizontal section, 18t and 12t of crude oil are added to make the drilling fluid , The oil content of drilling and completion fluid is 8% to 10%, and is fully emulsified with a certain amount of SN-1 solid emulsifier (or SP-80), supplemented by 2% to 3% FT-1 (WFT-666) and SMP improvement The quality of the mud cake makes it have good lubrication and anti-jamming capabilities. The filter cake friction coefficient Kf is always controlled below 0.029, the tripping resistance is generally 4t~8t, and the rotation torque is 300~450mV.
5.3 Wellbore purification technology
The main method is to choose drilling fluids and drilling completion fluids with strong rock-carrying ability. At lower displacements, the stick shear and flow The main adjustment for denaturation is to supplement MMH positive glue (or PMHC) and NH4PAN glue, so that the dynamic cutting force is greater than 15 Pa, the dynamic plastic ratio is about 1, the initial cutting is generally 18 to 23 Pa, and the initial cutting and final cutting are close; Engineering Measures such as short tripping and rotating drilling tools were taken in a timely manner. During the construction of this well, drilling, logging, and plugging were all completed at once, and the pump was turned on normally, ensuring that the entire horizontal section did not pass through the well once, and everything underground was Normally, there is no obvious drilling cuttings returning even after large-displacement well cleaning, which proves that the wellbore is clean and no obvious cuttings bed is formed.
5.4 Reservoir protection technology
Before entering the horizontal section, fully adjust the drilling fluid properties, control lower solid content and filter loss, and use a disposable mixing funnel to press Add 0.75% ~ 1.0% oil-soluble resin and 3% QS-2 during the cycle, and add sulfonated asphalt to make the content reach 2% ~ 3% to implement the technology of shielding and temporary plugging to protect the oil and gas layer, and replenish it in time according to consumption . Further strengthen the mud cake quality and reduce the amount of filtrate intruding into the oil layer. At the same time, the wellbore purification and solid phase control are strengthened to reduce the particles in the drilling fluid from entering the pores of the production layer and avoid blocking the oil and gas channels.
5.5 Solid phase control
Solid phase control mainly uses vibrating screens, cleaners, centrifuges, etc., coupled with frequent tripping operations, to provide drilling fluid density, solid phase Content control and performance maintenance bring a certain degree of difficulty. To this end, we have taken effective measures such as making full use of existing solid control equipment, increasing the amount of glue added, improving the rock-carrying capacity of drilling fluids, reducing the degree of repeated grinding, and reducing the content of fine particles, so as to effectively reduce the sand content. Control it within 0.2%, and control the solid content between 11% and 13%.
6 Field application effects
In the construction of 7 wells drilled in Tahe Oilfield, MMH positively charged polysulfonate-mixed drilling fluid and composite metal ion polysulfide-mixed drilling fluid were mainly used. Oil drilling fluids have their own characteristics when used on site. During the drilling operation, wells TK106H and TK201H were accident-free wells, while other wells suffered from stuck pipe accidents to varying degrees. Its performance is shown in Table 2. MMH positively charged polysulfonate-mixed drilling fluid has poor temperature resistance, making deep well maintenance difficult. Since MMH positively charged glue has poor compatibility with other types of treatment agents, the use of anionic treatment agents weakens the positivity of the system, thereby reducing the system's ability to inhibit collapse and prevent collapse. However, the MMH positively charged glue system has a strong rock-carrying ability. , to prevent the formation of "drilling chips bed" and ensure smooth tripping. The composite metal ion polysulfonate mixed oil drilling fluid has temperature resistance, compatibility, good rheology, and stable drilling fluid performance.
6.1 The use of MMH positive gel system in TK104H and TK201H wells
Before drilling in this well section, first convert the drilling fluid into the MMHSN-2 drilling fluid system in the casing , to make the MMH content reach 3% (colloid). Due to the severe blockage in the upper stratum of this well section, anti-collapse agents 3% PN-1 and 2% FT-1 were added to the casing at one time, and 8% was mixed into the casing when drilling to the deflection section. % crude oil, and add a sufficient amount of solid emulsifier SN-1 to fully emulsify the crude oil. During the drilling process, MMH, crude oil, PAM, and anti-slump water loss agent are regularly replenished at a certain depth to ensure that each component of the drilling fluid reaches the design requirements.
When the well inclination angle reaches 60°, strengthen short tripping and staged circulation, raise the drilling fluid YP to above 15Pa, control the dynamic-to-plastic ratio between 0.8 and 1.2, and control the static shear force Raise it to 8~10Pa/10~12Pa to ensure that the drilling fluid has strong carrying capacity and suspension ability. During the construction after the horizontal section, the solid content, especially the sand content, is strictly controlled. Make full use of the four-level solid control equipment and the method of replenishing glue to reduce the sand content in the drilling fluid to meet the design requirements.
Stable drilling fluid performance and appropriate rheology, strong anti-collapse ability and low friction coefficient, together with engineering measures, are the keys to the success of this section.
(1) Φ6 reading is not less than 8.5.
(2) During construction, the main focus is on maintenance, supplemented by treatment. The drilling fluid treatment agent is added in the form of glue to maintain stable drilling fluid performance.
Table 2 Drilling field performance of gradient and horizontal well paragraph
(3) Use SPNH and NH4-HPAN to adjust the drilling fluid flow pattern; Use SMP-1 and SPNH to control high temperature and high pressure water loss.
Rational compatibility of various treatment agents and good lubricity, strong anti-collapse ability and suspension carrying capacity are the keys to the success of this well's drilling fluid.
6.2 Usage of composite metal ion polysulfonate oil-mixed system in TK202H well
Before orientation, the polymer drilling fluid was converted into composite metal ion polysulfonate oil-mixed drilling fluid at one time. First add 40m3 of pre-prepared new slurry (1.5 t soil + 80 kg Na2CO3 + 50 kg NaOH + 75 kg PMHC). Then, use a mixing funnel to evenly add SPNH, FT-1, SMP-1, PA-1, and PMHC while circulating according to the formula, and then add an appropriate amount of Na2CO3. After the circulation is relatively uniform, 8% crude oil is evenly mixed within a large circulation cycle, and at the same time, 0.3% SN-1 solid emulsifier is added. Finally, sufficient circulation is carried out until the drilling fluid performance is basically stable.
During the drilling process, we always adhere to the main maintenance of glue replenishment. The principles for maintaining the performance of drilling fluids are: focus on wellbore purification, control rheology well, maintain appropriately high dynamic-to-plastic ratio and shear force to adapt to the special needs of carrying cuttings and effectively suspending cuttings, and control the mud cake well. Quality and lubricity, strengthen anti-collapse measures, and strictly control water loss. The selection and supplementary amount of various treatment agents vary based on normal drilling footage, lithology encountered during drilling, well inclination angle, operating conditions, etc. Generally, the glue replenishment time is within the first 1 to 2 weeks of each drilling trip.
6.3 Conclusion and understanding
Due to the effective and reasonable maintenance and treatment process adopted by the drilling fluid during the drilling of the deflection section and the horizontal section of the horizontal well, the drilling fluid has excellent performance and good construction results. The drilling fluid properties are shown in Table 2.
(1) Drilling fluid has strong ability to suspend rock and carry rocks, and the wellbore is clean
Drilling fluid has good rheology and has the characteristics of positive electrostatic glue, has good effect of carrying rock cuttings, and has strong suspension ability. The cuttings return is normal, and the suspended cuttings before drilling can be brought out on time every time the drilling is started; the cuttings are uniform, especially in large slopes and horizontal sections without any mixing phenomenon, with pure texture and clear edges and corners, reflecting The stratigraphic boundaries are clear, and the cuttings logging and electrical survey interpretation results are consistent.
(2) The drilling fluid has good anti-collapse performance, stable well wall, and regular well diameter
During the entire construction, although there were many tripping operations, the bottom hole working conditions changed greatly. , but due to the excellent performance of the drilling fluid and reasonable technological measures, the well wall is always stable. During the drilling cycle, it is rare to see flaked mud shale, and there is no phenomenon of well wall collapse, instability, and drilling. The vibrating screen Basically, all the drill cuttings screened out by the mesh were drilled, and every drilling trip went smoothly without any abnormality. The average well diameter expansion rate is shown in Table 3, which better solved the common problem of block collapse in the Triassic hard and brittle mud shale formation. , the problem of serious expansion of well diameter, which beneficially ensures the smooth implementation of drilling construction.
Table 3 The well radial contrastive result of third opening drilling well paragraph about Tahe oilfield's horizontal wells
(3) Drilling The fluid has good lubrication properties
Due to the special effect of SN-1 solid emulsifier and reasonable crude oil content, the solid phase control effect is good, the drilling fluid mud cake is thin and tough, the friction coefficient is small, and Kf is always controlled Within 0.0143~0.029, friction and torque are reduced to the maximum extent. Drilling and tripping went smoothly, the electrical measurement and screen tube were unobstructed, and the bottom was reached in one go. The tripping friction was generally between 4 and 8 t, and the rotational torque was between 300 and 400 mV.
(4) Drilling fluid has stable performance and is easy to maintain and adjust.
Although the pure drilling time is short and tripping is frequent during the entire construction process, only glue fluid is used for each drilling trip. Simple maintenance adjustments, no major processing required.
(5) Drilling fluid has a good effect in protecting oil and gas layers
The technology of shielding and temporary plugging to protect oil and gas layers has been reasonably implemented, with small filter loss and API water loss within 4.0ml. , high temperature and high pressure water loss is maintained at 9 ~ 11.0ml. Indoor evaluation results show that the composite metal ion polysulfonate mixed oil drilling and completion fluid system restores core permeability to an average of 92.2%, which not only better protects the oil and gas layer, but also prevents and plugs leaks.
(6) The composite metal ion polysulfonate-mixed drilling fluid has stable performance and is easy to maintain, making it an ideal drilling fluid system for horizontal well drilling.
References
[1] Fan Shizhong, Yan Jiannian, Zhou Dachen. Drilling fluid, completion fluid and oil and gas layer protection technology. Dongying: Petroleum University Press, 1996
[2] Xu Tongtai, Chen Leliang, Luo Pingya. Deep well mud． Beijing: Petroleum Industry Press, 1994
[3] Zhang Shaohuai, Luo Pingya, etc. Reservoir protection technology. Beijing: Petroleum Industry Press, 1991
Techniques of drilling fluid for horizontal well in Tarim
Jin Shubo Jin Pei Li Binwen
(Academy of planning and designing ,Northwest Bureau of Petroleum Geology,?rümqi 830011)
Abstract: Drilling fluid of deep horizontal well we should consider well hole stabilization technique, well holerefine technique, high temperature stabilization technique, lubrication and defend clip technique mostly. The MMH polymer sulfur mix with oil and resumed lubricate hydronium polymer sulfurixm with oil are used in horizantal well,TaHe oil field.This paper introduces two system which are used in field and application effects.
Key words: drilling fluid well hole refinement well hole stabilization lubrication reserve protection temporary jam technique