Inverting the rock mass P-wave velocity field ahead of deep buried tunnel face while borehole drilling

Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detection(DPD)system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod,geophones at the tunnel face,a laser rangefinder,and an onsite computer.A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling.A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method.Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet.A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained.Both the borehole core and optical image validate the inverted P-wave velocity field.A numerical simulation of a checkerboard benchmark model is used to test the tomography method.The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.

Assessment of the Behaviour of Surface to Borehole EM Telemetry in Horizontal Well

Hydrocarbon exploration has evolved over the years from shallow subsurface to deep subsurface prospecting in both onshore and marine environment.In accordance,technical development has encouraged exploration of unconventional reservoirs and development of deeply buried ones.The deeply buried carbonate reservoir in the Tarim Basin have attracted considerable attention(Lee,1985;Neil,1997;Jin et al.,2009,2015).Such deeply buried reservoirs requires careful and accurate well landing and borehole navigation through multiple regions of HC accumulation and precise well closing process involving accurate selection of positions for screens and so on.

Application and reliability analysis of DPM system in site investigation of HK weathered granite

A drilling process monitor （DPM） for ground characterization of weathered granite is presented. The monitor is portable and can be mounted on a hydraulic rotary drilling rig to record various drilling parameters in real time during normal subsurface investigation. The identification method for dominative and subsidiary interfaces has been established. The study reveals that the monitored drilling parameters are dependent on geotechnical materials and can be further applied to characterize ground interfaces. The t-test between manual logging and DPM logging has been carried out. The results show that the DPM has high accuracy in interfaces detection and well agreement with the manual logging. The findings show that the device and data analysis method are of potential application in subsurface drilling exploration in weathered granites. It also seems to have prospective uses in the determination of orebody boundary as well as in the detection of geohazards.

Late Jurassic to early Cretaceous magnetostratigraphy of scientific drilling core LK-1 in the Lingshan Island of Riqingwei Basin,eastern China

The Sulu orogenic belt is an uplift zone that was formed in the Late Triassic.Several Jurassic to Cretaceous sedimentary successions have been recognized within the Sulu orogenic belt in recent studies,including outcrops that are considered to be related to the newly discovered Riqingwei Basin.This basin has been the focus of extensive study due to its continuous Cretaceous rock sequence,geological location and petroleum resource potential.However,the lack of a consolidated chronology for the strata has precluded a better understanding of stratigraphy,tectonic evolution and resource potential of the Riqingwei Basin.Here,we present the results of a new magnetostratigraphic study of the continental scientific drilling borehole LK-1,which is located on Lingshan Island,offshore Shandong province,eastern China.The goals of this study are to(1)refine the Late Jurassic to Early Cretaceous chronostratigraphic framework of the Riqingwei Basin,and(2)investigate the location of the J/K boundary in the Borehole Core LK-1.The observed patterns of the paleomagnetic polarity zone in the LK-1 borehole correlate well with the geomagnetic polarity time scale(GPTS),and the continuous magnetostratigraphy profile defined in this core indicates an age ranging from 146.5 to 125.8 Ma for the samples interval.The sediment accumulation rates(SAR)of LK-1 show one period of high SAR(~10.5 cm kyr^(-1))at 135.3–130.6 Ma and two periods of low SAR(~4.8 and~2.2 cm kyr^(-1))at145.7–135.3 and 130.6–125.8 Ma,respectively.In addition,the magnetostratigraphic results suggest that the Jurassic-Cretaceous(J/K)boundary of the LK-1 is located within the magnetozone N21.2 n(~1254 m).This comprehensive geochronologic framework provides a good correlation of the marine Upper Jurassic to Lower Cretaceous strata in the Riqingwei Basin to other marine strata and continental sequences,in addition to providing a foundation for the study of the structural evolution of eastern China.

Uncertainty quantification and reduction in the characterization of subsurface stratigraphy using limited geotechnical investigation data

Subsurface stratigraphy is critical to the design,construction,and subsequent performance of geotechnical structures.However,in practice it is impossible to identify the stratigraphy of a subsurface geological domain with absolute certainty,due to the limitations imposed by geotechnical investigation techniques and project budgets.This paper presents a subsurface stratigraphic modeling and uncertainty quantification approach,which is established based on an improved and extended geological modeling technique previously established by the author and others,for simulating the stratigraphy of both two-dimensional(2D)and three-dimensional(3D)cases with more complex geological features.Furthermore,this approach provides quantitative evaluation of the amount of stratigraphic uncertainty in the current interpretation and enables the systematic reduction of stratigraphic uncertainty through the investigation of additional targeted borehole drilling locations.Illustrative examples,including artificial cases as well as two real cases from existing geotechnical projects,are presented in this study to demonstrate the use of the proposed analysis approach.

Smart system for safe and optimal soil investigation in urban areas

This paper discusses the challenges and diffculties experienced during soil investigation in urban areas using drilling machines and soil sampling.The focus is on the consequences of a lack of data on the subsoil profile and presence of utilities,which could cause major accidents with severe economic and social losses,resulting in constriction activities being delayed and urban services being disrupted.This paper describes certain accidents related to soil investigation in Qatar and their consequences,as well as the lessons learned from these accidents.In order to meet the challenges of soil investigation in urban areas,this paper presents a solution based on smart tech-nology,which includes:(i)a geotechnical information system with update data concerning the soil profile,soil surface,utilities locations,and water table level;(ii)tools for data management,analysis,and visualization;and(iii)a user interface that allows authorities,com-panies,and citizens to access authorized data via a graphic interface,update data,and send messages and alerts in the case of any inci-dent occurring.Finally,the paper presents a promising perspective for the development of smart drilling devices,which record data related to the functioning of a drilling machine and transmit data to the smart soil investigation system.