A Research Of Drilling Technique In Dagang Oilfield

Drilling drilling engineering geological parameters is try to know and master the objective conditions, these objective conditions mainly including geological tectonic characteristics, formation stress, formation pressure and formation collapse pressure and fracture pressure is closely related to the drilling engineering and formation factors, has become Cheng sea area of key technical problems of drilling development. Ii oil field sea situation, based on the research of reservoir physical properties, according to the drilling characteristics of blocks, mainly analyzes the reasons of formation collapse, and put forward the formation collapse prevention plan. Combined with drilling fluid selection and drilling tool combination optimization research, ultimately form a set of mature drilling technology, and guide the drilling construction of the block.Through research Cheng sea area is located in the south of dagang oil field sea area Cheng fault terrace zone, north of qikou sag in north and south for sheep two oil fields and cooperation development zone is located in the zhang dong zhuang structure, tectonic movement intensity, the structural evolution stage experience intense subsidence and depression expansion, change of formation pressure is bigger, Cheng sea area of complex fault block as the abnormal high pressure in the west and the east subject area (zhang hai.5) as the normal pressure system uneven formation pressure, pressure prediction is difficult, etc. Cheng sea area as a whole is an anticlinal structure, by zhang dong fault and sea4Wells fault is divided into north and south two broken nose, belongs to low porosity, low permeability reservoirs, the sand a with dolomite reservoir is given priority to, partial to contain calcium higher fine sandstone and silty sand rocks.Formation pressure system consists of the overlying rock pressure, formation pore pressure, formation fracture pressure and collapse pressure, quasi lateral prediction of formation pore pressure is the precondition of predicting formation collapse pressure and fracture pressure. For carbonate formation pore pressure prediction is relatively hard to this problem, this paper set up conversion coefficient model accurately reflect the real value of drilling fluid density. Borehole wall stability is one of the key technology of drilling, drilling and is a worldwide difficult problem. According to the properties of the soft ground, the corresponding preventive measures are given, stabilizing the borehole wall in drilling construction plays a pivotal role. Borehole wall stability problem not only exists in sand mudstone profile, but also often encountered in the carbonate rock profile. Carbonate rock profile of borehole wall instability mainly concentrated in the imbalance of initial formation, fractured formation and poor cementation of easy broken formation.Cheng2sea area is studied by this project characteristics, according to these characteristics, complex from the accident prevention, drilling fluid selection and optimization of processing, assembly, prevent formation collapse, etc., puts forward a set of optimized drilling technology for this block. Focuses on the stability of the block wall. Combining with the characteristics of block, from the aspects of mechanics and chemistry, the block hole collapse is studied. Since2007through the Cheng sea area of39Wells in construction of research situation analysis (more than just a well not complex accident, well due to borehole wall collapse card drilling, reaming, drilling tools such as malignant accident, the worst have to casing window sidetracking), theoretical calculation, the formation pore pressure and collapse pressure, leakage of contrast, predicting formation pressure with the actual drilling fluid density contrast, the influence factors of actual operation and so on, expounds strata borehole wall collapse reasons, and put forward the corresponding measures. According to the properties of the soft ground, the corresponding preventive measures are given, stabilizing the borehole wall in drilling construction plays a pivotal role. At the same time, the selection of drilling fluid system, key performance requirement, bit selection and optimization, the reasonable selection of assembly, have put forward the reasonable point of view. Formed a set of adapt to dagang oil field sea two OuDeYou drilling technology. To follow-up the production of the well construction speed, complex accident prevention, the implementation of the optimized drilling has great significance.Through investigation the root cause of the borehole wall instability, understanding is due to the hole formation around the borehole ground stress in the process of change, cause stress concentration, borehole rock will produce plastic flow caused by reducing; Brittle rock will cause falling collapse, caused by hole enlargement. When the borehole drilling fluid column pressure is higher than that of formation fracture pressure, sidewall rock tensile damage and lost circulation. When the rock tensile strength, the formation of resistance to tensile stress ability, then well drilling fluid column pressure lower limit decrease accordingly. Borehole wall stability according to the mechanics theory, when the borehole drilling fluid column pressure is lower than the formation collapse pressure, the collapse of the wall rock pressure value is greater than the formation stress, and at the same time less than the fracture stress of formation, won’t appear sidewall instability phenomenon, can think, mechanics factors of borehole instability directly caused by the drilling operation. Safe drilling fluid column pressure range is wide, when drilling borehole wall will be more stable. As a result, drilling fluid density value is reasonable measure in the process of drilling borehole wall is an important factor of stability, to improve and establish a study block formation breakdown pressure section profile, formation pore pressure and formation collapse pressure profile, determine the reasonable drilling fluid density, which make the drilling process has a certain predictability, to improve the drilling speed and drilling safety is very important. By the multi-port well drilling practice, we have found a phenomenon:find the timing of the borehole wall collapse, always during drilling, and few collapse occurred in the drilling process. During the process of drilling, drilling fluid column pressure and circulating pressure loss, and lapping of drilling tools, enough to balance the formation colla.pse pressure. But in stop cycle, after the drill, due to reduced circulating pressure loss, again due to the effect of drill pump, resulted in the instability of borehole wall. So, from this caused by sidewall instability, should further improve the density of drilling fluid, to compensate for circulating pressure loss and draw up the pressure loss.The thesis studies on the borehole wall collapse, covers many aspects, such as mechanical, chemical, comprehensive analysis, the comprehensive summary, put forward a set of comprehensive on-site operation scheme of borehole wall stability. Combination of assembly selection and optimization, drilling fluid selection, focus on the performance of drilling fluid, for homework in Cheng2sea area, provides a complete set of construction scheme.