| Exploration and exploitation object of the right bank of the Amu Darya gas field becomes more and more complex, the drilling is more and more difficult. It needs study high-efficiency drilling technology to resolve the technical bottlenecks of drilling engineering. There are 4 main challenges in drilling operation in this area: ①The geology and reservoir condition are very complex. The reservoir is carbonatite formation with developed pore and fracture and long interval salts and gypsum formation. So there is high risk during drilling. ② The overlying rock layers are very thick salts and gypsum formation and the thickness is usually 400-1200m. So it is very difficult to control the well track of horizontal wells.③ The geologic structure in this area is very complex and its scale is small. There are several high salt water formations, salts and gypsum formation, loss formation, collapse formation and faulted anticline zone. "Three High"(high pressure, high production and high H2S) gas resovoir and loss formation are in the same formation. This needs high requirement to drilling performance. ④ Because of above mentioned complex geology condition and low recovery of core in the completed wells, the core technology in this area shall been increased.Through collecting and analyzing the geology and drilling data of drilled wells in the right bank of the Amu Darya gas field and combining with the mature technology for "Three High" wells in others fields, the technical solution and testing program has been made. By systematic theoretical study and field test, the main achievements in this paper are shown as following:(1) Through building creep mechanics model, the lithology and creep law in this erea has been mastered and the mud density window has been determined. Meanwhile the mud system formula with good rheological behavior, strong anti-sloughing ability, resistance to pollution of salt gypsolyte has been developed and field process has been drawn up. Through detecting and forecasting collapsed pressure, the direction and value of hole collapse, direction of in-situ stress and three pressure profile can been confirmed. Also this can provide a basis for optimization of casing program and technical solution for borehole instability.(2) The horizontal wells in this area adopted hole structure of "three spudding and three completion". By this method, different pressure system and huge thick gypsolyte above reservoir can been isolated. The wellbore trajectory is recommended to adopt "seven segments" profile. This can not only meet the requirement of field operation and deal with all kinds of down-hole problems and accidents, but also decline the drilling cost.(3) A set of leak sealing technique has been put forward. These techniques can be used in all kinds of loss conditions.(4) A kind of low solid content mud system has been optimized. This mud system has a function to reduce reservoir damage. The formula of this mud system is water+2%DFD-140+2%CMJ-2+1%JYW1+0.2%VP+0.4%ABSN+2%SMP-2+NaCl (NaCl is replaced by formate while the mud density is more than 1.2) (0%～saturation condition)+ superfine calcium carbonate +0.5～1.0% Zn2(OH)2CO3+NaOH (adjust pH to 10-11). This Mud system can resist 150℃ or more,20% salt,5% calcium and 20% cuttings contamination. API filtration rate of this mud sytem is less than 3mL and high temperature and pressure (150℃) filtration rate is less than 15mL. The yield value via plastic viscosity of this mud system is more than 0.5 whenever normal or high temperature. The permeability recovery value of this mud syterm is more than 90%.(5) Based on BXQX coring tool, a kind of new coring tool has been developed, which can adapt to fractured carbonate rock formation. In the meantime, a kind of natural diamond core bit has been researched. Through field test, the coring operation program which adapt to fractured carbonate rock formation in Turkmenistan has been put forward.In this paper, the requirement of exploration and development in the right bank of the Amu Darya gas field is the main start point of research. Close combining with actual condition in field, the technical bottlenecks in drilling engineering has been resolved. In the end, a set of drilling technology that is suit for "Three High" gas field has been developed and integrated, which include directional and horizaontal drilling technology, safety drilling technology for coexistence of blowout and mud losses in the same interval, reservoir protection technology and coring technology. The production of single well, success rate of drilling and ROP will improve significantly in the right bank of the Amu Darya gas field after this set of drilling technology is used. This can provide powerful technical surpport for safe and efficient exploration and development in the right bank of the Amu Darya gas field. |
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