Xiude, Lu (CNPC Downhole Service Company of CCDC) | Dengsheng, Ye (CNPC Downhole Service Company of CCDC) | Juhui, Zhu (CNPC Downhole Service Company of CCDC) | Dan, Song (CNPC Downhole Service Company of CCDC) | Congbin, Yin (CNPC Downhole Service Company of CCDC) | Guan, Bin (CNPC Downhole Service Company of CCDC) | Guigang, Guigang (CNPC Downhole Service Company of CCDC)
Multiple new technologies of stimulations have been successfully developed and used in domestic low permeability reservoirs over the last few years. A new staged fracturing technique with bottom annular packer on coiled tubing (CT) has been extensively used in the fields of Sichuan. This process employs a new bottomhole tool assembly (BHA) on the CT, which offers the opportunity to achieve hydro-jet perforating, annular packing and fracturing multiple pay zones with a single entry of the CT string. This technique has proven effective in stimulating thin interbedded reservoirs individually to open pay zones and improve gas production optimally. Following the final CT stimulating stage, the well is cleaned out and for subsequent production. This paper describes the unique features of the coiled tubing staged fracturing technology with bottom annular packer. Case studies of seven well are presented on this paper. The key procedure controls and surface process enhancements during the applications of the new CT stimulation technique will also be analyzed and summarized.
Key Words: Coiled Tubing Packer Staged Proppant Fracturing
Zhang, Wei (Xinjiang Oilfield Company) | Mao, Xinjun (Xinjiang Oilfield Company) | Yang, Hong (Xinjiang Oilfield Company) | Wang, GuoBing (PetroChina) | Wang, Zhi Yue (Yangtze University) | Ruan, Ran (Yangtze University) | biao, Ruan (Yangtze University)
The rock in deep strata of Wuxia area in Junggar Basin is abrasive and with low drillability. Part of the formation sections with abundant fractures, which leads to mud lose frequently. The exploration progress has been slowed down by low drilling
speed and accidents. The exploration department of Xinjiang Oilfield Company preferred underbalanced drilling technology on well F8 and A1 on the basis of feasibility analysis of UBD technology in Permian strata. The applications reduced lose
circulation effectively and promote the rate of penetration considerably.
Well F8 and A1 used foam and nitrogen as underbalanced drilling circulation medium respectively. The wellbore sizes are 215.9 mm. The rate of penetration in underbalanced drilling sections are quintuple than conventional rotary drilling. It saved
more than 20 days in the overall drilling time. The conversions between foam/nitrogen with mud were successfully once only. There was no losing circulation during underbalanced drilling progress.
The successful application of underbalanced drilling technology in deep strata of Wuxia area solved the deep drilling speed improved problems entirely. It reduced mud lose and promote drilling speed. The drilling overall time and exploration cost
has also been decreased greatly. The innovation application provides a new method for deep drilling speed improved in this area.
In the passed drilling, the ROP of advanced cone and PDC bits was nearly 0.65 m/h, and the ROP was no more than 0.92 m/h even with turbodrills and impregnated bits. However, the ROP of underbalanced drilling section has promoted several times than conventional drilling. ROP optimizing was substantial versus direct offset wells that experienced quintuple drilling time through the same formation. With this success, the team has accumulated valuable experience of deep drilling for Junggar Basin.
Liang, Xing (Schlumberger) | Lou, Ji Sheng (Schlumberger Offshore Svcs) | Zhang, Yong Qiang (Schlumberger) | Zhang, Jie Hui (Schlumberger) | Zhang, Lei | Song, Ju | Halomoan, Parlindungan Monris | Habib, Rana Khalid | Yu, Daiguo | Bisain, Amarjit Singh
A shale gas play operator in Central China has commenced horizontal well drilling development. Upon completion of multiple vertical pilot or evaluation wells, the shale gas target reservoir zones have been identified and are to be developed with horizontal wells. Due to the difficulties and risks associated with acquiring wireline measurements in horizontal sections, Logging While Drilling (LWD) measurements along with Rotary Steerable Drilling Systems (RSS) are used to provide real time formation evaluation, allow the well to be placed optimally within the target reservoir, reduce drilling risks, improve rate of penetration and help optimize completion design.
An integrated LWD tool and RSS was run for the first time in a horizontal shale gas well. The LWD tool delivers elemental spectroscopy, formation sigma and sourceless neutron along with the conventional triple-combo measurements of gamma ray, density, thermal neutron and resistivity. The system provided:
1. Improved lithology determination and enhanced formation grain density evaluation from elemental capture spectroscopy. This led to improved porosity determination and completion design
2. Optimized lateral placement in the best quality sub-layer with near-bit GR and density images
3. The ability to avoid drilling hazards through real-time monitoring of the drilling parameters available from the LWD tool
4. Greatly improved ROP through the improved drilling capabilities of the RSS. This minimized the time that the formation was exposed to drilling fluids before measurements were acquired. These measurements provided the information required for the success of the first horizontal drilling in a shale gas play.
This paper will detail the use of LWD measurements and a RSS drilling system for an integrated shale gas solution providing comprehensive petrophysical evaluation, accurate well placement, and drilling efficiency optimization for the first horizontal
well drilled in a shale gas play in Central China.
Song, Xianzhi (China University of Petroleum Beijing) | Li, Gensheng (China University of Petroleum Beijing) | Huang, Zhongwei (China University of Petroleum, Beijing) | Zhang, Laibin (China University of Petroleum, Beijing) | Tian, Shouceng (China U. of Petroleum Beijing) | Cui, Liu (CNPC Drilling Research Institute)
Horizontal wellbore cleanout by rotating jets has been developed rapidly in the past decade. However there are few investigations on mechanism and characteristics of the high pressure water jet impacting and annular helical flow, which are two primary powers to break up the consolidated bed, lift and suspend particles, and increase the wellbore cleanout efficiency. To realize the characteristic of helical flow, the pathilines of rotating high pressure jets and annular velocity distributions were
investigated firstly in this paper. The results indicated that the motive power to form the annular helical flow is the non-uniform cross flow generated by partial lateral jets which impact on the wall at an angle, while other jets provide the fluid sources. Further, base on the particle trajectory model and liquid-solid mixture model, the motions of particle, the annular distribution of sand velocity and concentration in annular helical flow were carried out. The pathlines of sand were spiral curves around the drill pipe in the annular helical flow, which can enhance the sand moving ability and increase the horizontal wellbore cleanout efficiency finally. The influences of flow rate, particle size, nozzle assemblies on the annular helical flow strength and sand transportation efficiency were analyzed comprehensively. Finally, the downhole tool was designed according the theoretical results and has been tested in hundreds wells in China. The test showed that it can greatly improve the oil and gas well production and reduce the operating duration. This paper is beneficial to investigate characteristic of sand sweeping by annular helical flow and optimize the tool structure, operation parameters.
Assessment of drilling performance during Casing Drilling and optimization of the process has been achieved using an existing computer simulator, which has not been tested before in Casing Drilling applications while its value has been proven
in conventional drilling. The simulator allows prediction of ROP using standard drilling data of WOB, RPM, flow rate, and formation parameters. Use of simulator post drilling allows fine tuning it to match drilling performance so that future jobs in the same field could be more optimally designed.
Different lithologies along the wellbore were defined in terms the rock type, strength, and abrasivity from drilling data collected while Casing Drilling of a 2000 ft well in Haynesville shale, where ROP was high in the upper part but fairly low in
the lower part. Rock strength data normally is not given and estimation was made from databases for similar rocks while they could be estimated from sonic data if available.
Running the simulator allows for re-drilling the well utilizing all basic data and trying to match the real drilling time curve and the measured ROP. Good matching was achieved for the drilling depth-time and also ROP values were matched well over the whole depth interval. Using the simulated model, WOB and RPM were optimized to increase the ROP at the lower part of the well. The results proved that the simulator can simulate Casing Drilling effectively as it has proved its value for conventional
This work shows that the simulator can help the driller to use historical data of Casing Drilling and then by applying different scenarios, e.g. increasing WOB or RPM and he can apply them while drilling a new well to obtain higher ROP. Using the
simulation results, optimal drilling parameters can thus be found for drilling future wells in similar geologic environments.
Surfactants systems have been used in oil well drilling and completion fluids for several decades and have been used for numerous applications, including emulsification of brine for invert emulsion fluids, emulsion prevention in completion fluids, wellbore clean-up in spacer trains, flowback enhancement in drill-in fluids, etc.
In recent years, the use of specialized designer surfactant blends to remove formation damage and dramatically improve production in cased hole and open hole completed wells has prompted field personnel to expand the range of target applications of this technology.
The aforementioned specialized surfactant blends have several unique functional characteristics that make them ideal for multiple uses in the field. Generally, these systems solubilize oil, remove oil from surfaces, remove emulsions, water-wet and disperse solids, reduce interfacial tension and mobilize in-situ fluids.
With a full understanding of the mechanistic ways that these surfactant blends function under downhole conditions and when confronted with various operational issues in the field, this technology was successfully used to free stuck pipe, to free blocked completion screens of heavy oil sediments and to prepare a well for water injection.
This paper presents some of the technology associated with specialized designer surfactant blends and the case studies where the technology was applied in the field to enable project successes.
Yan, Zengxuan (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Xu, Hongwei (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Liu, Guanghui (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Li, Qinghong (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Wang, Jianhong (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Ma, Xianping (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Zhao, Feng (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Li, Qingyu (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Yang, Shiquan (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited) | Sun, Lin (Qinghai Drilling Company of CNPC Xibu Drilling Engineering Company Limited)
Installation occupies a small area, the 735hp (4,000m) plateau mountain rig can meet the requirement of drilling operation in plateau mountain area with complex topographic conditions and is characterized by low operation cost, low oil consumption and good economical efficiency.
Introduction (issues and contents)
Operation areas of Qinghai Oilfield located in Qigequan, Nanyishan, Huatugou (the south and north of the mountain) and Yingdong plateau mountain areas, etc. are of dry weather, insufficient oxygen and complex terrain, which make the pre-drilling works hard to be conducted. Moreover, such conditions lead to small wellsites, bumpy roads (with a max. gradient of 30°), difficult demolition and resettlement. Therefore, there is no rig applicable for such areas operation.
Statement of Theory and Definition (main part of the paper):
Overall scheme of the rig
The rig is a mechanically driven drilling rig. The facilities in the back part of the derrick substructure is driven by an integral seven shaft chain box compound , while the turntable is driven by AC frequency conversion motor independently. The diesel engine and the pressure coupler are evenly arranged on the 0.8m-high back substructure, adopting an integral chain box compound , respectively drives the mud pumps, winches, energy saving generator which provides the power to turntable motor through VFD. The winch is installed in the back of the derrick substructure (low installation). The main brake is hydraulic disc brake while the auxiliary brake is aircooled electromagnetic eddy current brake. The height of rig floor is 7.5m and the clearance height is 6.3m. Except for the winch, the mud pump and the compound box, all components are less than 20 tons. The vertical-lift derrick assembly includes 6 sections, each section of which shall be assembled on the ground firstly and then be lifted by hydraulic winches as a whole for installation. The derrick is tightly installed on the base of the substructure, meeting the requirements of 250 tons top drive system.
Advantages of mountain rig
The mountain rig is high reliable and fit the operations below 4,000m, using AC frequency conversion motor to drive the rotary table. The easily controlled rotary speed which has 0-300r/min stepless speed regulating and wide variable speed range, and the torque of rotary table have the heavy overload capability of dealing with downhole incident. The operating cost is 50% lower than the 735hp all-electric drilling rig.
The rig is inserted vertical-lift derrick occupies small area and, suitable, for drilling operations in complex terrain areas.
The rig using hydraulic pressure coupler, power-saving electric generator and other energy saving equipment has low fuel consumption and good economical efficiency.
Tao, Dong Zhen (China National Petroleum Corporation) | Long, Jing Zhang (China National Petroleum Corporation) | Zhi, Lai Bi (China National Petroleum Corporation) | Zhi, Wenza (China National Petroleum Corporation) | Zhang, Xiao Long (Schlumberger) | Ying, Tom Kang Xiao (Schlumberger) | Downie, Simon (Smith Bits) | Ke, Colin (Schlumberger) | Li Jun, Jim Zhao (Schlumberger) | Hong Yong, Mike Zhang (Schlumberger) | Liu, Xiao Jun (Schlumberger)
The operator must reduce deviation tendencies in the 8-1/2" vertical hole section drilling the difficult J2x formation to efficiently develop gas reserves in Turfan basin, China. The challenge is to maintain near perfect perpendicular hole trajectory from 2400-3500m while drilling interbedded sandy claystone and coal layers. In the worst case scenario, the operator is forced to make several costly correction runs before starting the horizontal production hole. To solve the problems, engineers experimented with pendulum and steerable motor BHAs to maintain wellbore vertically with limited success.
Most recently, Kekeya wells Ke28 and Ke33 required 6-5 bits/trips respectively to complete the 8-1/2" hole section at unacceptably low average ROPs of 1.6 m/hr and 2.4 m/hr. The operator required a PDC/deviation control tool to maintain verticality and increase ROP. To accomplish the objective, the drilling team utilized a rock strength program and a bit/BHA modeling system to investigate several different cutting structures to determine the best blade count and cutter placement configuration. Based on the study, a six-bladed 8-1/2?? PDC bit was identified as the best candidate to accomplish the objectives. To mitigate deviation tendencies, a reliable automatic vertical drilling system (VDS) was selected. The reliable VDS tool does not require a MWD logging sub and can be deployed during normal drilling operations including backreaming and shoe drillout.
The new-style 8-1/2?? PDC bit was run in combination with VDS on new well Ke282 with outstanding results. The bit/VDS bottom hole assembly drilled the entire 740m section at 7.1 m/hr through the difficult J2x formation in a single run setting a new field benchmark. The optimized PDC bit increased ROP by 250% while reducing trips/bit consumption by 82%. The performance improvement saved the operator more than 14 days of rig time for a total cost savings of $93,000 USD.
Wellbore stability is important for successful horizontal and extended reach drilling (ERD) wells. Hole instability problems associated with ERD wells can sometimes change the original development plan because of complications and unforeseen
operational and geomechanical issues.
This paper presents a case study from offshore Vietnam, where historically, no significant wellbore stability problems had been reported for vertical and low-angled wells. There were plans to develop the field by drilling highly deviated and ERD
wells from one platform. However, instability problems and significant non-productive time from frequent pack-offs, tight holes and stuck liners were encountered while drilling one of the designed wells. The hole was sidetracked three times and finally drilled at a lower angle than originally planned.
Geomechanical analysis using core, well log, drilling data and experiences were used to build a field scale geomechanical model characterizing the in situ stress, pore pressure and rock mechanical properties in both the overburden and reservoir
sections. Stress-induced borehole failure observed in image logs from an offset well and diagnostic analysis of failure mechanisms from cavings recovered from the problematic well provided significant insights into the likely nature of instability problems in the ERD well. Hole instability problems were attributed to the failure of weak bedding planes and anisotropic rock strength in the shales interbedded with sandstones. To control the weak bedding and anisotropic failure, stronger mud weights were needed than were in the original plan. The required mud weight for maintaining stability varies depending on wellbore trajectory and bedding characteristics. The usagee of high mud weights is unfavorable because of possible formation damage that could occur and the risk of fracturing the reservoir (because of lower fracture gradient). Consequently, the original ERD plan had to be revised and new optimum well trajectories designed that took into account any drilling issues, in addition to completion and productivity requirements.
Introduction and Objectives
The field studied is within the southern Nam Con Son Basin, offshore Vietnam, and has a water depth of ~95 m. The main reservoir is a repetitively stacked series of early Miocene age shales and sandstones at depths of more than 3000 m TVD ss,
which has traditionally been subdivided into seven principal reservoir sand cycles capped by shale. These zones are generally correlatable across the region and are approximately 15 to 45 m. Historically, there have been no major stability issues while drilling in this region because of the relatively low stress magnitudes. During drilling of vertical exploration wells no borehole integrity issues were encountered.
Field development was planned with several incline wells from one central platform with deviations between ~40 and 85°. Some well designs encompassed challenging depths and angles. A previous wellbore stability analysis suggested all the
wells could be drilled with mud weights less than 11.2 ppg. However, the development drilling was hindered by severe stability problems such as pack-offs, tight holes and stuck liners, encountered while drilling one of the first high-angle wells. The hole was sidetracked three times and finally drilled at a lower angle than originally planned.
Xu, Yonggao (Changqing Oil Field Res. Inst.) | Zhao, Zhenfeng (PetroChina) | Wang, Yajuan (Oil and Gas Research Institute, Changqing Oil Field, PetroChina) | Zhang, Yanming (China National Petroleum Corp.) | Ma, Xu (PetroChina Co. Ltd.)
Changqing sandstone tight gas is characteristic of low-permeability and low-pressure, which is difficult to obtain economic benefits without fracturing. A new multistage fracturing technology for horizontal gas well is used in tight sandstone gas
reservoirs. The new technology is hydro jetting-based and control the nozzles by opening the sliding sleeve by ball setting .With no need of packers and slugs, the technology realizes the integration of perforating, fracturing and isolation, achieving fracturing multiple stages in a single trip.
Field trials of 64 wells show that the new technology is simple and reliable, which is capable of meeting the requirements of rapid isolation and multi-fracturing in gas wells. The new technology opens another door for multistage fracturing horizontal
well of sandstone tight gas and make the reservoirs have economic development potential.