Well Abyed-2 is an exploration well in Block 1 of Yemen.The formation is geologically complex.There is weathered crust in the interface between Mukalla group and Hashiyate group,and a high pressure zone between Sab'atayn and Meem formation.In air drilling of surface section,wellbore sloughing resulted in drill pipe stuck;the broken drillstrings fell into well during dealing with drill pipe stuck.All these caused the abandon of this well.Considering oil and gas show at lower section,the well was redrilled after moving the rig and sidetracked.The drill pipe stuck occurred again in the sidetracked operation.The fall of fishing tool during accident dealing process made the condition further complicated and caused the abandon of this well.This paper details the two accidents and the reasons for failure of accident treatment.The experience and lessons learned from this well provide reference for smooth drilling of follow-up wells.

Rabaa-1 is a key exploration well drilled in Block 71 in Yemen.5 spuds was schemed in the well and after Φ216 mm hole drilled,Φ127 mm DP with liner running tool got stuck during Φ177.8 mm liner cementing operation.After this incident happened,drilling experts of SIPC EP Yemen immediately made feasible technical procedure and took effective measures to deal with the difficulties by means of the actual down-hole conditions.According to these technical measures,it took 14 days to conduct the wash-over and back-off fishing operations and altogether 193.4 m of down-hole fishes with liner running tool finally had been pulled up.Liner cement incident has been successfully diminished not only saving the life of the high output oil-well,but also giving a good lesson on liner cementing operator in Yemen.

合成基钻井液（SBM）以其特有的环保性能及机械钻速高、井壁稳定性好等特点,已成为国际上海上油气钻探的常用钻井液体系。但是在深水钻探作业中,由于温度和压力对流变性的影响常导致井漏和当量循环密度（ECD）不易控制。为了解决该技术难题,近年来国外首先研制出一类新型的具有恒流变特性的合成基钻井液（CR-SBM）,其流变性,特别是动切力、静切力和低剪切速率下的黏度等参数基本上不受温度压力的影响。阐述了该新型钻井液的典型组成及性能特点,对比了传统SBM和CR-SBM在不同温度、压力下的流变性、抗岩屑污染和毒性测试结果,并介绍了国外CR-SBM的现场应用情况。

AbstractDesign of drilling fluids is crucial to extended reach drilling (ERD) with the challenges including borehole stability, hole cleaning, lubricity and equivalent circulating density (ECD) management. Normally, oil-based drilling fluids would be the best choice for an extended reach well with a horizontal displacement of 8000m. However, the Liuhua Oilfield is located in the South China Sea, an environmentally sensitive area. It is necessary to develop the high performance water-based drilling fluids which offer the performance to match oil-based drilling fluids.The integrated design proposal of water-based drilling fluids for the well Liuhua 11-1-B3 ERW4 with a horizontal displacement of 8000m (26247ft) is discussed in this paper, including design criteria, the formulations and the parameters of performance of the drilling fluids in each interval of the well. The more attention is paid to the 12 1/4-in. open hole section, where a kind of high performance water-based mud (HPWBM) is prepared. The two newly developed chemical additives, an amine polymer and an aluminum complex, are added in the KCl/polymer drilling fluid which was successfully used in the extended reach wells with a horizontal displacement of 6000m in this oilfield. In addition, a membrane-forming agent is added in this mud system and an optimized combination of lubricants was used to improve the lubricity of the drilling fluid.Numerous experiments were conducted to evaluate the various properties of this novel water-based drilling fluid. The experimental results indicate that it has excellent rheological properties, very low filtration rate, good lubricity and strongly inhibitive character to shale, which are very close to the commonly used oil-based drilling fluids.The results of risk analysis show that the design proposal of this water-based drilling fluid is feasible and can meet the drilling requirements of ERD with a horizontal displacement of 8000m open hole section in this area with less pollution of the sea and without increasing more cost.

The effects of pressure and temperature on drilling fluids are considerable at high temperature and high pressure. There is a big error if the static pressure at the bottom hole was calculated with parameters of drilling fluids at stand condition,and kick,blowout or lost circulation may occur in wells with small margins between pore and fracture pressure. This work started with establishing the model for predicting the temperature distribution profile of drilling fluids inside the drill string and in the annulus during circulating,then laboratory tests were conducted and the density property of oil-based drilling fluids was investigated. Based on the test,mathematical model for predicting the density of both oil-based and water-based drilling fluids has been established,and the correlation coefficients are higher than 0.99. Mathematical models for predicting the equivalent static density of drilling fluid have been established by combining the temperature model during circulating and density model. The Prediction models can provide theoretical basis for managed pressure drilling technology,it is significant to control downhole pressure properly and prevent problems and accidents.

A significant error will be generated in calculating the equivalent circulation density (ECD) of high temperature deep wells if drilling fluid rheology measured at surface was used. For wells with small differences between pore pressure and fracturing pressure, this error may lead to kick, blowout and/or mud losses. A model was established to predict the HTHP drilling fluid density, equivalent static density, rheology and ECD, based on the downhole temperature fields of wells in circulation. The model gave prediction that was highly consistent to measured values (with correlation coefficient being greater than 0. 99). this model can be used in well pressure management and control, and is helpful in the prevention of downhole troubles.

This paper discusses the systematic design and development of low-damage drilling fluid to protect the low-permeability gas reservoir of the Sulige block in the Ordos Basin, Inner Mongolia Autonomous Region, China. Based on investigation of the geological characteristics and the potential formation damage of the Permian formation of the reservoir, waterblocking due to invasion of drilling or completion fluids was identified one of the most severe causes of damage to gas well deliverability. By adopting the phase trap prevention method, ideal packing theory, and film-forming technology, a low-damage drilling fluid, sodium formate brine containing efficient waterblocking preventing surfactants, optimized temporary bridging agents (TBAs), and film-forming agents has been developed. The performance of the new drilling fluid was evaluated by using a variety of techniques. The results show that the fluid has good rheological properties, good strong shale-swelling inhibition, good temporary plugging effect, ultra-low filtration, and good lubricity. It can efficiently minimize waterblocking and can be used to drill horizontal wells with minimal intervention of the reservoir in the Sulige Gas Field.

The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 °C using the RheoChan 7400 Rheometer. The experimental results show that the apparent viscosity, plastic viscosity and yield point decrease with the increase of temperature, and increase with the increase of pressure. The effect of pressure on the apparent viscosity, plastic viscosity and yield point is considerable at ambient temperature. However, this effect gradually reduces with the increase of temperature. The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells. On the basis of numerous experiments, the model for predict the apparent viscosity, plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis. It is confirmed that the calculated data are in good agreement with the measured data, and the correlation coefficients are more than 0.98. The model is convenient for use and suitable for the application in drilling operations.

The creating mud cake with ultra-low filtration with drilling fluid requires the match between the pore throat size and the temporary shielding/plugging agents(TPA) particle size.A new scientific and reasonable TPA optimizing method is developed."1/3 bridging rule" and "temporarily plugging/shielding technology" mainly based on mean formation pore size works effectively for homogenous reservoir,while is difficult to seal large size pore throats in heterogeneous reservoir.Based on "the Maximum Packing Efficiency Principle","Ideal Packing Theory" and "the D90 rule",a new graphical method to optimize plugging particle size distribution was proposed,and the associated software was developed which can quickly and accurately select and recombine TPA with different particle size in a given proportion based on formation correlative parameters,such as pore throat size data.Field tests shown that drilling fluids and well completion fluids composed of optimized TPA can create fine mud cake effectively,seal pore throats with different size in heterogeneous formation.Consequently it can prevent the solid particles and filtrate of invasive fluids from entering formation.Compared with conventional temporary bridging method,this new method has smaller invasion radius(<2cm),and higher return permeability(>83%),a lower breakthrough pressure gradient(1.05MPa/m),and better reservoir protection.

To determine the damaging mechanism of the Jurassic reservoir in Tarim Basin,which is a low porosity,low permeability and high pressure reservoir,laboratory studies were done based on the reservoir structure,lithology,porosity-permeability nature and mineralogy.It was shown that the major damaging factors were water block(accounting for 70%~90%) and stress-sensitivity(accounting for 25%~60%).To protect the reservoir,several drilling fluid additives with specific functions were selected to formulate a drilling-completion fluid with strong encapsulation and inhibitive capacity.The application of the fluid in a high pressure deep exploration well was successful: the API fluid loss was 1.0 mL,the HTHP fluid loss was 1.8 mL,and the permeability recovery was greater than 85%.By preventing the formation of water block,the permeability impairment of the reservoir was minimized.Combined with appropriate engineering measures,this fluid can be used in drilling the consolidated sand stone formations with coal-bed layers.

Low-permeability dense reservoirs, including micro-fractured reservoirs, are commonly characterized by high content of clay substances, high original water saturation, high sensitivity to invasive fluids, high capillary pressure, complicated structure and anisotropic, high flow-resistance and micro pore throats etc,. Generally they also have lots of natural micro fractures, probably leading to stress sensibility. Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations. Once damaged, formation permeability can rarely recovered. Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%. Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed. Also some feasible precaution or treating approaches of water-blocking were put forward. In a laboratory setting, a new multi-functional drilling fluid composed mainly of amphion polymer, sulfonation polymer, high effectively preventive water-blocking surfactants, ideal packing temporary bridging agents (TBA) and film-forming agents, etc., were developed. New low-damage drilling fluids has many advantages, such as good rheological properties, excellent effectiveness of water-blocking prevention, good temporary plugging effect, low filtration and ultra-low permeability (API filtration⩽5 mL, HTHP filtration⩽10 mL, mud cake frictional coefficient⩽0.14, permeability recovery>81%), can efficiently prevent or minimize damage, preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability, the only one developing integrated condense gas field. Some references can be provided to similar reservoir formations.

In order to approach the mechanism of enhancing plant growth by new fungal activator protein,the effect of activator protein with different concentration on physiological characteristics of soybean was studied.Compared with control after 7 d treatment with 1,2 and 5μg mL~(-1)activa- tot protein,root activity of soybean was increased by 44.2%、54.5% and19.8%,and nitratereduc- tase activity was increased by 61.33%、138.37% and 53.2%,respectively.Compared with control after 15 d treatment with 1,2 and 5μg mL~(-1) activator protein,the content of chlorophyll in leaves was increased by 12.56%,17.32% and 5.32%,the content of soluble sugar was increased by 18.56%,31.02% and 18.69%,and the content of soluble protein was increased by 17.36%, 31.96% and 23.10%,respectively.In conclusion,after plants were treated with activator protein of different concentration,the physiological indexes related to plant growth were all enhanced to different degree,and the effect of 2μg mL~(-1)activator protein was of best efficiency to the plant.

Many technical challenges exist in formation damage control in the deep exploration wells in the north fault formation of Chaidamu Basin in Qinghai Oilfield,including without typical core data,formation lithology and physical properties,the existence of high pressure formation saturated with gas or water,the existence of several formation with different formation damage theory in different formation.The sensitivity studies for the formation in this area were conducted using Artificial Neural Network.Based on these results,the bridging agents were optimized using the "Ideal Packing Theory",and a kind of polymer-sulfonates drilling fluid formula for formation damage control were determined through a lot of experiments.The field tests show that the drilling fluid has better performance,such as better rheological properties,higher temperature resistance,lower API filtration and lower HTHP filtration rate,thinner and slicker mud cake.The results of formation damage control are obvious.The formation permeability recovered up to 82.54% and the skin factor is less than 1.5.In addition,the wellbore is more stable without any problems such as hole sloughing,tight hole and reaming.The safety,high quality and fast drilling have been achieved.

A HTHP rheometer, Fann50SL, has been used to measure the HTHP rheological properties of a kind of high-temperature high-density water based drilling fluid. The experimental analysis indicates that the apparent viscosity (AV), plastic viscosity (PV), and gel strength (Gel) of that drilling fluid will decrease with temperature, and the decrease amount will become smaller with the temperature increased. And the regressed results suggest that the best model suitable for HTHP rheological properties of this drilling fluid is Casson Model. Based on these investigations, a mathematical model used to predict the apparent viscosity of drilling fluid at HTHP conditions is established. The calculation results have proven the accuracy of this model. It is recommended to better use Casson model to conduct matching analysis of rheological properties of HPHT drilling fluid.

The well Kun-2,with its total depth of 5950 m,is an important exploratory well on the structure Kunteyi-1 of the Qaidam Bain.In order to discover and protect payzones,this study optimized the temporary plugging agent and the temporary plugging planning according to the ideal packing method,the newest advancement in reservoir protection studies.And through large amounts of experiment,this study determined a proper drill-in fluid system.The field tests showed that the optimized drill-in fluid used for the 4th spud-in is effective in reservoir protection,in addition having good rheological property and lubricating effect,and being helpful for wellbore stability.This new temporary plugging agent could help 87.5% of the permeability of the payzone to be recovered,with the surface coefficient of less than 1.5,which was proved to have obvious effect on reservoir protection.No wellbore instability problem occurs when this plugging agent was used in this area,which demonstrated its advantage in the wellbore stability.This paper recommends its wide use on well sites.

In order to approach the mechanism of enhancing plant growth by new fungal activator protein,the influence of activator protein with different concentration on physiological characteristics of many crops were studied.the testing results showed that soaking the seeds of cotton in 2-3 μg/mL new type activator protein for 6 h could significantly promote the germination vigor and germination rate of seed,The testing results showed that soaking the seeds of tomato and loofah in 1 μg/mL new type activator protein for 6 h could significantly promote the germination rate of seed,The testing results showed that soaking the seeds of cucumber in 500,1 000 new type activator protein could significantly promote the germination rate of seed.

Sealing core drill operation can protect the core by using closed fluid to avoid pollution and soak by drilling fluids, and obtained geologic information can really reflect the formation characteristics. At present, well Puguang 2 is the deepest well in sealing core drill in China. During sealing core drill operation, there are some technology difficulty existence, such as high formation pressure, high density H_2S, high temperature in bottom hole, high circulation pressure, long open interval, etc. Through adopting corresponding technique measures, sealing core drill operation is finished successfully in well Puguang 2.

详细叙述了国内外硅酸盐钻井液研究应用现状,包括硅酸盐的抑制性、硅酸盐钻井液的防塌机理、硅酸盐钻井液的研究情况和应用情况,最后介绍了笔者对硅酸盐钻井液的研究情况及认识.