Ultra-deep well drilling in foreign countries started earlier. 1984, the former Soviet Union drilled the world's first ultra-deep well cγ-3 in kola peninsula, with the depth of 12260m and the second sidetracking 199 1 to 12869m, which still holds the record of the world's deepest well. The United States has successfully drilled several wells with a depth of 9000m, such as Rogers 1, with a depth of 9583m；. 1 Well has been logged with a depth of 9 159 m; ; Well Francci 1-9 with a depth of 9043m; ; Well Zmmalon 2, with a depth of 9029 meters, was scientifically drilled by KTB in Germany, with a depth of 9 10 1 m.
3. 1.2 Borehole temperature
Well Cγ-3 in kola peninsula, the former Soviet Union, with a bottom hole temperature of 215℃; High temperature geothermal scientific drilling in Lake Salton, USA, with a depth of 3200m and a temperature of 353℃; Germany KTB scientific drilling, the well temperature is 280℃; Well WD- 1A in Gegentian Hot Area, Japan, with a depth of 3729m, once encountered ultra-high temperature stratum at 500℃.
3. 1.3 high temperature treatment agent
Deep and ultra-deep well drilling started earlier abroad. In the 1960s, the viscosity reducer of ferrochromium salt with salt resistance, calcium resistance and 150 ~ 170℃ was successfully developed. In 1970s, sulfonated lignite, sulfonated tannin, sulfonated phenolic resin and their condensates with sulfonated lignite were successfully developed. The temperature resistance of these treatment agents is mostly between 180 ~ 200℃. At the same time, low molecular weight polyacrylate which can improve high temperature rheology and medium molecular weight polyacrylate which can reduce high temperature filtration were also developed. Due to the thermal oxidation degradation of lignite products at high temperature, the drilling fluid is thickened after being polluted by salt and calcium, and the filtration loss reduction effect is reduced; Polyacrylate contains no chromium and has good thermal stability, but poor tolerance to divalent cations; Sulfonated phenolic resin needs to be used with sulfonated lignite to achieve obvious effect, but the effect of temperature resistance and salt resistance is limited. For this reason, foreign workers have conducted extensive and in-depth research since 1980s, and developed many high-temperature mud treatment agents with temperature resistance exceeding 200℃.
Dickert developed two kinds of high-temperature resistant filtrate reducer with AMPS, AM and N- vinyl -N- alkyl amide (NVNAAM) as raw materials, and both of them have good filtrate reducer effect when the temperature exceeds 200℃. The drilling fluid system composed of them has the best comprehensive performance in the range of pH 8 ~ 1 1.5.
Patel, USA, uses AMPS as polymerization monomer and N, N ′-methylene bisacrylamide (MBA) as crosslinking agent, and forms water-based drilling fluid filtrate reducer at high temperature by controlling crosslinking. The filtrate reducer has good temperature resistance and excellent calcium and magnesium resistance at 400℉(205℃), and is an excellent filtrate reducer for high-temperature water-based drilling fluid.
Thaemlitz et al. developed two new drilling polymers and used them as main agents to obtain a new environmental protection and high temperature resistant water-based polymer drilling fluid system. The system is mainly used for high temperature and high pressure drilling, and the temperature resistance can reach 232℃.
With vinyl amine (VA) and vinyl sulfonic acid (VS) as raw materials, a new generation of high temperature filtrate reducer Hostadrill 4706 with temperature resistance over 230℃ was obtained by * * polymerization. Laboratory tests show that this filtrate reducer with a relative molecular weight of 5×105 ~10×105 has outstanding salt resistance (it still has good performance in saturated brine) and can significantly improve the rheology of drilling fluid.
Polydrill is a high-temperature filtrate reducer introduced by BASF (formerly SKW) in Germany, and similar products are sold by Baker Hughes in the United States. It is a sulfonated polymer with a relative molecular weight of about 2× 105 and a temperature resistance of 260℃. Polydrill can not only keep the rheological stability of drilling fluid or completion fluid system, but also resist the influence of various pollutants on drilling fluid performance; Polydrill has outstanding salt tolerance, which can resist KCl and NaCl to saturation, and its calcium and magnesium content can reach 4.5×104 ~10×104 μ g/g.
Mil-Tem is an anti-high temperature filtrate reducer produced by ARCO. Sulfonated styrene (SS) and maleic anhydride (MA) have a relatively small molecular weight of 1000 ~ 5000, and the temperature resistance can reach 229℃.
Pyro-Trol and Seal of Kyoto Electronics Industry Co., Ltd. are two kinds of filtrate reducer for high temperature drilling fluid developed by Baker Hughes Company, both of which are patented products of the company. Pyro-Trol is the * * * polymer of AMPS and AM, while Seal of Kyoto Electronics Industry Co., Ltd. of Japan is the * * * polymer of AMPS and N- alkyl acrylamide (NAAM). Usually used together. The field application results show that both of them have good high temperature stability and can be used in high temperature formations at 260℃.
M-I Drilling Fluid Company has developed a new polymer, which is an effective filtrate reducer under high temperature and high pressure. Hostadrill4706 is a filtrate reducer based on vinyl sulfonate and vinyl amino compound, and its temperature stability is as high as 230℃.
3. 1.4 drilling fluid system
3. 1.4. 1 Drilling fluid system for scientific drilling in the former Soviet Union
The former Soviet Union mainly used two kinds of drilling fluid systems, namely, high-temperature resistant low-density polymer drilling fluid system and high-temperature resistant high-density polymer drilling fluid system.
(1) High temperature resistant low density polymer drilling fluid system
In kola peninsula Cγ-3 ultra-deep well, high temperature resistant and low density polymer system is used to drill crystalline rock. See table 3. 1 for system components.
Table 3. 1 Components of Low Solid Polymer Mud System Used in kola peninsula
(2) High temperature resistant and high density polymer drilling fluid system
Well TK SG-6 is 7502m deep, 7025m well temperature is 205℃, and abnormal formation pressure is1.85g/cm3. High temperature resistant and high density polymer drilling fluid system is adopted, and its components are shown in Table 3.2.
Due to the early start of scientific deep drilling in the former Soviet Union, many excellent additives such as polymers have not been used in the drilling industry. Therefore, in order to adapt to the complex geological conditions such as well depth and well temperature, its mud system has the characteristics of high solid content, various additives and large dosage.
Table 3.2 Composition of high-density polymer mud system for TNK ultra-deep wells
3. 1.4.2 Drilling fluid system for KTB scientific drilling in Germany
Drilling fluid for KTB well is divided into pilot well and main well. Dehydrated high-temperature solid-free drilling fluid is used in the pilot well. D-HT is a silicate compound with stable rheology at high temperature, but it loses a lot of water and is corrosive. On this basis, artificial hectorite clay Hostadrill 3 1 18 is added into the main hole, which is called D-HT/HOE system. After the well depth is 7 100 m, the mud performance becomes worse, the mud viscosity decreases at high temperature, it is difficult to carry cuttings, and the hole is enlarged. After the research of Krasztel University, it is transformed into D-H/HOE/Pyrodrill system, and its composition is shown in Table 3.3.
Table 3.Composition of 3D-H/Hoe/Pyrodrill Drilling Fluid System
After conversion, the low shear viscosity of mud increased, the high temperature water loss decreased, and the chip carrying capacity increased, but the funnel viscosity and high shear viscosity increased to an unacceptable level (FV≥240s until the flow stopped).
At first, the drilling fluid manager of KTB well only paid attention to rheological stability and adopted D-HT solid-free modified silicate drilling fluid. During drilling construction, the performance became worse, the borehole wall collapsed, and it was difficult to carry cuttings, so it had to be transformed into a drilling fluid system to control water loss at high temperature. Sulfonated polymers and * * * polymers are widely used. At high temperature (280℃), the rheology of the system is unbalanced, the ability to carry cuttings becomes worse, the solid phase can not be controlled, and the borehole wall shrinks seriously (geologists explain it as rock flow). Finally, shut in the well in advance at 9 10 1m (designed well depth 10000m).
American scientific drilling 3. 1.4.3 drilling fluid.
1974, the United States drilled the deepest well in the world-Rogers 1 well in Oklahoma, with a depth of 9583m m. Due to the abnormal mud density, the pressure in the well was out of control, which induced a blowout, and the formation fluid was mainly sulfur, which quickly solidified in the well, ending the well. 1985, a scientific drilling hole (SSSDP plan) centered on studying high-temperature geothermal was conducted in S2- 14 hole in salton, with a depth of 3220m and a ground temperature of 353℃. The Bayes well 1988 is 1762m, and the bottom hole temperature is 295℃. Drilling fluids used for drilling high temperature wells in the United States mainly include:
1) polysulfonate drilling fluid system, such as DURATHERM water-based drilling fluid system provided by Magcobar company, is mainly composed of clay, PAC, XP-20 (modified lignite) and Resiner (special resin), and its pH value is10.5 ~11.
2) Sepiolite polymer drilling fluid: Using sepiolite soil instead of clay, the temperature resistance is obviously improved.
3) Dispersed lignite-polymer drilling fluid system: developed by Chevron Service Company, 7178.04m was successfully drilled in Mississippi waters, and the bottom hole temperature was 2 12.8℃.
4) Drilling fluid for scientific drilling in Japan
According to Japan's "Deep Drilling Mud" (Shouhong Sano), Japan basically uses dispersion system instead of polymer components. It is recommended to use lignosulfonate mud, which is characterized by high temperature resistance, strong inhibition and large solid phase (cuttings) bearing capacity. Its main components are shown in Table 3.4.
Table 3.4 Mud System Used in Drilling High Temperature Geothermal Wells in Japan
The system has very good temperature resistance, but the materials containing chromium ions in the components have an impact on the environment.
In recent years, Japan has studied and used water-based drilling fluid with temperature above 265,438+00℃. The drilling fluid is mainly composed of two ultra-high temperature materials, Therma Vis and G-500S, plus wall-building agent, high-temperature filtrate reducer, wellbore stabilizer and high-temperature lubricant. Using this system, 6300 meters deep well drilling was completed in the "Mishima" base, and the bottom hole temperature was 225℃.