Abstract: A high performance gel strength enhancer was developed for use in oil base drilling fluids to improve their suspension capacity.The enhancer is a polyester made from a high purity dimeric dibasic acid and a polyoxyethylene fatty amine(EthomeenC25).The molecules of the gel strength enhancer have flexible backbones and groups of strong polarity, which enable the molecules to form steric networks.The gel strength enhancer effectively improves the low shear rate rheology and gel strengths of oil base drilling fluids.LSYP of drilling fluid is incresed from 0.51 Pa to 3.07 Pa, gel strength is improved from 1.5/2.5 Pa/Pa to 5.0/7.5 Pa/Pa.High density oil base drilling fluid has been formulated with this gel strength enhancer, and the properties of the drilling fluid tested.The drilling fluid has good basic properties and high gel strengths, and has good suspension capacity even after hot rolling at 180℃.
Abstract: Nano SiO2 particles of uniform size were prepared using the improved Stober method and their surfaces functionally modified to render the SiO2 gas wetting.The effect of the wetting nano fluid on the wettability of rock cores was studied using different methods such as angle of contact measurement, Owens method and imbibition method.The studies show thatcores with ultra-strong gas wetting can be made by adding 1-2 mL of ethyl orthosilicate and ammonia, and 0.3% of FG24.Prior to and after treatment of cores with the nano gas wetting fluid, the angles of contact of water and oil on the cores are increased from 23° to 157°, and from 0°to 135, respectively.Imbibition experiments showthat, prior to and after treatment of cores with the nano gas wetting fluid, the water and oil saturations of the cores are reduced from 87% to 3.5%, and from 73% to 32%, respectively, and the imbibition rates of water and oil are reduced from 0.26 mL/min and 0.27 mL/min to 0 mL/min within 2 h.These data indicate that the nano gas wetting fluid has good wetting transition capacity.
Abstract: Organophilic clays commonly available for use in white oil and diesel oil do not disperse well in bio-diesel oils which have different molecular structures than those of the white oils and common diesel oils.JHA, an organophilic clay, was recently developed through laboratory study.The base clay selected for the study is the Xiazijie Na-bentonite, and four kinds of organic intercalating agents(ESDS, SSDS, LSDS, and BSDS) were tried in the study to replace the interchangeable cations in between the crystal layers of clays.The ratio of the concentration of clay slurry to that of the intercalating agents is 3:1.JHA has colloidal rate of 98%.To make JHA, the optimum temperature for the reaction should be kept at 70℃, the time for the reaction is 1h, and the selected intercalating agent is ESDS.A mud made with 3.0% JHA in bio-diesel has yield point of about 5 Pa, API filter loss of 21 mL, and remains stable at 180℃.Characterization of JHA with XRD and FTIR shows that the c-spacing of JHA is remarkably increased, and symmetric and asymmetric stretching vibration peaks of-CH2-are observed, indicating that the intercalation agent has been successfully inserted into the crystal layers of bentonite.
Abstract: Oil base drilling fluid has long been used in horizontal drilling in Yulin gas field to combat borehole wall collapse.A viscosifier used in drilling fluid was developed from dimeric dibasic acid and diethylenetriamine, and was characterized by IR.Laboratory evaluation shows that oil base drilling fluid treated with this viscosifier has AV, PV two times those of the base drilling fluid, both before and after hot rolling, while the electrical stability voltage remains almost unchanged.This viscosifier has been successfully used in field operation.
Abstract: The Nanpu buried hill oil reservoir(Jidong Oilfield) is characteristic of deep burial at 4, 000-5, 600 m, high formation temperature(4.22℃/100 m, and 223℃ atbottom hole), low formation pressure(pressure coefficient 0.96), and developed fractures.The produced oil has high gas/oil ratios.A high temperature low density low solids content drilling fluid and a high temperature gel plug have been developed for use in reservoir drilling in Nanpu.The high temperature drilling fluid retains its good performance at 220℃, and the gel plug functions at 170℃.In formulating the high temperature low density low solids drilling fluid, two tetra-polymers were chosen as the high temperature viscosifiers and high temperature filter loss reducer, respectively.SMP, SPNH and a high temperature sealing agent, FT3000, were also used to improve the properties of the drilling fluid.A high temperature oil-in-water drilling fluid was formulated with two emulsifiers, HWZR and HWFR, (both are high temperature stable and salt resistant) a viscosifier HVF-H and two high temperature filter loss reducers, HWFL-H and HVS-H.The two drilling fluids have good performance after aging at 220℃ for48 h, and densities ranging between 0.98 g/cm3 and 1.08 g/cm3.Using the gel plug, oil and gas zones are isolated and protected during pipe tripping and casing tieback.The high temperature low density low solids drilling fluid has been used in 8 wells, the oil-in-water drilling fluid used in 13 wells, and the gel plug used in 2 wells, all proved successful in reservoir protection.
Abstract: Calcium chloride(CaCl2)-Alkyl polyglucoside(APG) drilling fluids have low water activities compatible with the water activities in shale formations, and this makes it easy to reach osmotic equilibrium between the drilling fluids and the shale formations, In hot rolling tests, the first and secondary shale cuttings recoveries of the CaCl2-APG drilling fluids are higher than 90%, almost the same as that of oil base muds.Shale crops from Block Jiaoshiba have their strengths slightly reduced after soaking in the CaCl2-APG drilling fluids.CaCl2-APG drilling fluids of 1.20-2.00 g/cm3 have extreme friction coefficient the same as that of oil base muds.CaCl2-APG drilling fluids, afteragingfor 72 hours at 130℃, still retain their properties.When contaminated with drill cuttings at concentrations less than 15%, the properties of the drilling fluids still keep stable.Laboratory study shows that the CaCl2-APG drilling fluids are suitable for use in shale gas horizontal drilling in Jiaoshiba.
Abstract: The Well Jia-3-21 X is located in the Jia-3 fault in the northwest of the Gaojiapu structure in Huabei Oilfield.The well penetrated several faults.The ShahejieFormation penetrated is consisted of long section of salt and gypsum interlayers.Borehole collapse, mud losses, tight hole and sticking of wireline logging tools and drill pipes have occurred during drilling operation.A bionic drilling fluid, capable of strengthening the borehole wall, was introduced to solve these problems.In laboratory studies, NaCl was introduced into the bionic drilling fluid to enhance its inhibitive capacity.Hot rolling test with salt rocks gave cutting recovery of 85%, and gypsum rocks gave cutting recovery of 95%.Contamination by 0.6% CaCl2, had only slight influence on the properties of the fluid.Field application of this drilling fluid on the Well Jia-3-21 X was very successful, with average hole enlargement decreased by 62%, and time of drilling greatly shortened.
Abstract: A polyamine micro foam drilling fluid was formulated for use in drilling porous or fractured low pressure formations where mud losses had frequently occurred, and in combating well collapse and reservoir damage.The density of the polyamine micro foam mud can be controlled within 0.43 g/cm3-1.15 g/cm3 by adjusting mixing speed, optimizing the use of weighting additives and viscosifiers, and adjusting pH of the mud.The micro foam mud can be used in these conditions such as high temperature(120℃), 12% NaCl, 12% clay of poor quality, or 21% diesel oil contamination.Polyamine used in the mud can inhibit surface hydration and osmotic hydration, and the ability of polyamine to reduce surface tension and to form semi-permeable membrane on the surface of borehole wall makes it superior in borehole instability control and reservoir protection.
Abstract: A seawater base annular space protection fluid, CP-02.was developed for use in offshore drilling in Bohai oilfield where fresh water is in shortage on platforms.The formulation of CP-02 includes some additives selected through laboratory experiments, such as the biocide YHZWJ-15, scale inhibitor BHF-701 A, and corrosion inhibitor BHH-509, which is suitable for use in seawater.One example of the formulation is as this:Seawater+0.5% YHZWJ-15+0.01% BHF-701A+0.01% thiocarbamide+0.5% BHH-509.The rate of corrosion of the CP-02 to oil well pipes is as low as 0.005, 1 mm/a, indicating its good performance in protecting oil well pipe strings.
Abstract: Lingshui 17-2 gas field in the deep water area in South China Sea has reservoir formations that are controlled by these parameters:formation pressure coefficient 1.19, average porosity 31.5%, range of permeability 0.08×103 μm2-2.512×103 μm2, averaged at 633×103 μm2, and clay content 16.1%.The porosity has regular relation with permeability, and the clay is sensitive to salt contamination and water flow.When transfer an exploration well to a production well, the test fluid to be used shall satisfy these needs such as balancing the formation pressures, inhibiting the generation of gas hydrates, and protecting reservoirs.A test fluid formulated with "aquo complex" was used in the gas field, giving gas production of 1.60×106 m3/d, and skin factor as low as 0.2.
Abstract: Borehole wall destabilization in unconventional oil and gas drilling has been a problem frequently encountered, and it is widely agreed that plugging of the nano-micron fractures in shale is key to the solution of the problem.A new compound cellulosic filter membrane was chosen to do filtration test.This membrane has pore sizes that are compatible with the sizes of fractures found in shales.By comparing of spurt losses of different additives, the plugging effect of these additives on the membrane can be examined.Using this method, limestone of nano-micron particle sizes and silica of the same size distribution are selected and compounded, producing a clay-free drilling fluid with strong plugging capacity.Polyamine and aluminum compound are also introduced into the drilling fluid to render it inhibitive capacity.At low apparent viscosity, this drilling fluid has high YP/PV ratios, and high φ6, φ3 readings.These characteristics are advantageous to hole cleaning.The drilling fluid has low filter loss and high percent cutting recovery(almost 100%).It has plugging capacity much higher than that of the conventional polymer drilling fluids, and is suitable for use in tight oil and gas drilling and shale gas drilling.
Abstract: In drilling the Yan'an Formation(coalbeds) in Jinghe Oilfield, borehole instability has long been a problem.Analyses of the drilling and wireline logging data show that one third of the coalbeds have been moderately or severely collapsing during drilling, with average hole enlargement over 10%.It has been found that, the Yan'anFormation as a whole does not destabilize badly, most of the coalbeds are dull coals, which are generally stable and do not collapse.The collapse of the coalbeds during drilling has been caused by the lack of plugging and sealing capacity of the drilling fluid used, and the existence of fractured coalbeds and poor quality coalbeds with mudstone interlayers.
Abstract: A new FM super gel was studied for its performance and mechanism as a lost circulation material.As an LCM made from polymers that swell when water is absorbed in, and some rigid matrix materials, FM super gel retains its function at temperatures up to 140℃.The FM super gel can swell when mixed with water, thus seals channels through which mud is lost.In the studies, quartz sands(particle sizes 0.3-2.0 mm), steel balls(diameters 4.3-7.8 mm) and slat(with slits of 1.0-5.0 mm) were used to simulate fractured formations with high permeability and large pore throats.The FM super gel stopped mud losses on the three simulators when total mud losses were 86-113 mL, 204-382 mL and 22-64 mL, respectively, and the maximum pressure exerted on the FM super gel was7.0 MPa.When rigid particles, elastic particles, fibers and deformable fills were added to the FM super gel, the total volumes of mud losses through the steel balls and the slat were reduced to 63-95 mL and 15-43 mL, respectively, and the maximum pressure exerted on the FM super gel was increased to 9.0 MPa, indicating that the pressure containment was enhanced.The FM super gel was used in the well Nanpu-13-1170 and the well Daji-4-9-Xiang-4, and had gained great success in mud loss control, with no reoccurrence of mud losses.
Abstract: A testing device has recently been developed as a tool to determine parameters governing the sedimentation stability of cement slurry.Based on the idea that the longitudinal compressive strength of set cement should satisfy the need of well cementing, a method of determining the parameters controlling the sedimentation stability of cement slurry is presented.In this method, when the compressive strength of a section of the top set cement just satisfies the need of engineering for the minimum compressive strength of set cement, the corresponding difference between the density of the top and bottom of the set cement is taken as the control parameter for measuring the sedimentation stability of cement slurry.Simulation test shows that this device is easy to operate and gives reliable results.
Abstract: Gel strength method and hysteresis loop method are commonly used in the evaluation of thixotropy of cement slurry.These two methods have recently been studied.Taking field application of thixotropic cement slurries into consideration, it was suggested that the evaluation should cover mobility and progress of gel strength of cement slurry, and operation safety.Based on the study, a new evaluation method was developed, employing a high accuracy rotational viscometer to measure the shear strengths of cement slurry at different times in very low shear rates.The influence of shear force on gel strength is almost eliminated.Continual measurement can be realized through program control.Using this method, the change of gel strengths of cement slurry with temperature can be studied, thus helping develop better cement slurry formulation for field application.
Abstract: A filter loss reducer for use in oil well cement slurries was synthesized with(AMPS), N, N-Dimethylacrylamide(DMAA), 3-Allyloxy-2-hydroxy-1-propanesulfonic acid(AHPS) and acryl acid(AA).Molecular structure and thermal stability of the copolymer were characterized using IR and TG.Laboratory evaluation of the copolymer showed that API filter loss of a cement slurry(3%-6%) can be reduced to less than 50 mL.The copolymer functioned well at 180℃ or under contamination of the cement slurry by 36% of salt.Laboratory evaluation shows that the filter loss reducer control filter loss by changing electrical porperties of filter cake and increasing viscosity of cement slurry.Thickening time of the cement slurry was also slightly prolonged.
Abstract: Effects of re-dispersible powdered latex of the properties low temperature cement slurry were studied.It is found that the permeability of set cement can be remarkably reduced by adding re-dispersible powdered latex into the cement slurry, the bond strength of the interface between set cement and casing string/borehole wall at the same time is increased.At concentration of 4.0% redispersible powdered latex, the permeability of the set cement is reduced by 94.2%, while the bond strengths of the interfaces between set cement and casing string/borehole wall are increased by 66.4%and 84.1%, respectively.Addition of the re-dispersible powdered latex improves the micro-structure of the set cement and the interfaces, making them denser and smoother.At concentrations of less than 3%, the latex has less effect on the thickening time, mobility and compressive strength of the set cement.At concentrations greater than 3%, the latex to some extent viscosifies the cement slurry, and retards the development of the strengths of the cement slurry.
Abstract: A salt-resistant thickening agent, BCG-1S, was developed for use inseawater base fracturing fluids.The BCG-1S is made from acrylamide, unsaturated functional monomers DM16 and AMP1 through polymerization and hydrolysis, using ammonium persulfate-sodium bisulfite as initiator.Below 10℃ 0.55%BCG-1S viscosities in 10 min.Settlent rate of single particle is 0.0324mm/s at 30℃.The viscosified tap water or seawater can tolerate contamination of 4, 000 mg/L Ca2+ and 2, 000 mg/L Mg2+.A seawater base fracturing fluid is formulated with the BCG-1S, BCG-5(a metallic ion chelator), B-55(a viscosifier), B-13(a high temperature stabilizer) and BCG-10(an encapsulated gel breaker) etc.This fracturing fluid has good carrying capacity and high temperature stability(up to 140℃).No sedimentation of solid particles is found in the fracturing fluid sample at 25℃ after 7 d, and the viscosity of the fluid remains almost unchanged.The fracturingfluid, after gel breaking, has residue content of less than 5 mg/L and surface tension of less than 26 mN/m, indicating thorough gel breaking.The flow conductivity of the fractures generated by this fracturing fluid is only reduced by 8.45%by the gel breaker solution used, which is acceptable.
Abstract: The effect of viscoelasticity of thickening agent solution on the sedimentation rate of proppant particles was studied through static sedimentation test of a single proppant particle in the solution of thickening agent used in linear colloid fracturing fluids.Effort was made to explain the study results using characterization of the internal structure of the linear colloid fracturing fluid.It is understood that the sedimentation rate of a single proppant particle decreases with increase in viscoelastic modulus.Some linear colloids, such as hydroxypropyl guar gum(HPG) and FAG-500, a cellulose, appear to be more viscous, while XST239, a high temperature polymer, has viscosity that is equivalent to its elasticity.The sand suspension capacity of these three thickening agents is a mixture of the function of the viscosity and the elasticity of these agents, and thus has the maximum fitting correlation coefficient with the complex modulus G*.The fitting results are:lgu=-1.6928 lgG*+0.2468, lgu=-0.9214 lgG*-0.1824, lgu=-1.6928 lgG*+0.2468, lgu=-0.8307 lgG*-0.2132.Low concentration XCD solution is more of an elastic solution, and the sedimentation rate of proppant particles is determined by the elastic modulus of the solution:lgu=-2.0426 lgG'-0.1286.Characterization by FE-SEM shows that XCD solution has honeycomb structures inside it, and XST239 solution has dense lamellar structures in it, while in HPG and FAG-500 solutions, there are loose lamellar structures.
Abstract: CO2 energized fracturing fluid was studied on its use in the Heidi Temple block in Jilin Oilfield where reservoir formation pressure is low and the crude oil has high viscosity and high freezing point.Unlike conventional water based gel fracturing fluid, pure CO2 was used in the energized fracturing fluid to create fractures and to carry sands.This technology was successfully applied in fracturing the well Hei+79-31-45.This paper discusses the differences between CO2 energized fracturing fluid and conventional fluids regarding operation equipment, surface pipelines and operation parameters etc.
Abstract: Composite polyelectrolyte solution is studied for its use in fracturing fluid as thickening agent.It was found that stable homogeneous composite polyelectrolyte can be obtained by adjusting the molecular weights of anionic and cationic polyelectrolytes, and the cationic degreeof cationic polyelectrolytes.A cationic polymer with molecular weight of 800, 000 and cationic degree of 9.1%, when mixed with an anionic polymer with molecular weight of 22, 000, 000, produces a composite polyelectrolyte with high viscoelasticity, Study of the composite polyelectrolyte with SEM shows that network structures are generated in polyelectrolyte formed through Coulomb force, and the network structures vary with different polyelectrolyte morphology.Analyses of the rheology of the solution of a composite polyclectrolyte used in fracturing fluids show that it has excellent viscoelasticity, and the storage modulus is far greater than the loss modulus at a frequency of 0.1 Hz.Viscosity- temperature curves show that at shear rate of 170 s-1 and 130℃, the composite polyelectrolyte solution still retain viscosity that is greater than 40 mPa·s.Homogeneous composite polyelectrolyte is expected to be used to prepare a new fracturing fluid system,
Abstract: In deep water drilling, low temperature always causes increased mud viscosity which in turn leads to loss of mud over shale shakers.Other difficultiessuch as cuttings carrying in large-size holes, formation of gas hydrate, hydration and dispersion of shales, and lost circulation in narrow density windows sections of a well etc.are not uncommon, Solutions to these problems are presented in this paper.Also in this paper, the progress made in water base drilling fluids and synthetic base drilling fluids used in deep water drilling are summarized.Constant rheology drilling fluid for deep water drilling has recently made remarkable progresses.This drilling fluid is composed of emulsifiers, wetting agents, organophilic clay, polymer viscosifiers, and flow pattern modifiers.BP Company is the first company defining constant rheology drilling fluid with 4 parameters, which are PV/YP ratios at 4.5℃ and 49℃, the ratio of initial(10 s) gel strength and final(10 min) gel strength, and the ratio of the 10 min gel strength and the 30 min gel strength, BP's work provides guidance to the design of constant rheology drilling fluid.
Abstract: Lost circulation imposes the most serious damage to reservoir and is an arduous technological problem remained unsolved.To diagnose and control lost circulation, three elements to lost circulation, i.e., location in which mud is lost, type of lost circulation, and rate of mud loss, should be fundamentally understood.The mechanism and type of lost circulation are the prerequisite for selecting/making the reasonable lost circulation control technology.In lost circulation prediction, drilling data and geological data are the most important.Series of laboratory studies have been conducted to find a method for lost circulation diagnosis.Studies were conducted on the stress sensitivity of fractures and vugs, and the propagation mechanism of fractures.The deformation of channels into which mud is lost and the rate of mud loss can be predicted for the choice of best lost circulation materials.When lost circulation occurs, drilling parameters such as penetration rate and drill cuttings change correspondingly, and real-time mud logging data can be used to predict the status of lost circulation.In the diagnostic model developed, the type of lost circulation is diagnosed using circulating pressure when lost circulation occurs.Based on the understanding of the changing course of lost circulation, a preliminary diagnostic system for lost circulation is developed, providing theoretical support for lost circulation control.
Abstract: Viscous oil in the heavy oil zones in Venezuela is buried in shallow depths and the shale caps are unconsolidated.The reservoir formations have low pressure bearing capacity and are full of fractures.Conventional prepad fluids used in previous cementing jobs often resulted in lost circulations, making it difficult for the cement slurries to return to the designed depth.Cleaning of the annular spacing were generally poor during cementing, and cementation of the two interfaces(interface between casing string and cement sheath and the interface between cement sheath and borehole wall) is weak, resulting in annular channeling in thermal recovery and corrosion of uncemented casing string by acid gases such as H2S and CO2.The life of the production well is thus shortened.In field practices, it was found that by adding 25%sodium silicate solution into prepad fluid, lost circulation and discontinuity of cementing were prevented from occurring, the cement slurries in the annular space returned to the designed depth and the cement sheath was intact.Bond strengths of the two interfaces were enhanced.All these contributed to the prevention of casing damage by acid corrosion.The key point in cementing with sodium silicate prepad fluid is to prevent the sodium silicate from contacting with cement slurry, because the contact of the two will inevitably shorten the thickening time of the cement slurry and lead to cementing disasters.
Abstract: Structural fractures and micro fractures are highly regionally developed in the low pressure formations in Sulige gas field.This paper discusses the geological characteristics of the formations in the gas field in which mud losses are easy to occur.Case histories of mud loss control are studied based on the experiences gained through field practices.Several effective methods of mud loss control are presented in this paper, and are expected that they are of helpful in mud loss control in similar situations.
Competent Authorities：China National Petroleum Corporation Ltd
Sponsored by：CNPC Bohai Drilling Engineering Co. LtdPetroChina Huabei Oilfield Company
Address： Editorial Department of Drilling Fluid and Completion Fluid, Bohai Drilling Engineering Institute, Yanshan South Road, Renqiu City, Hebei Province