Pemanfaatan Wellbore Strengthening Agent Selama Pengeboran di Onshore Sumatera Bagian Utara Indonesia

At northern part of Sumatera Indonesian onshore many drilling issues were encounteredin the area, in particular the overlying shales above the pay zones in the high deviatedtrajectory wells. Since the last well drilling in this area was 70’ era, so that limited data isanother drilling engineering challenge, especially to provide an accurate drilling fluid. Tocombat the drilling issues, utilization of pre-treated wellbore strengthening agent wasapplied to reduce well bore issues and strengthen the well with an effective filter cake. In Northern Sumatera Indonesian onshore well in Indonesia was used as a case study. First a brief understanding and fundamentals of geo-mechanics is described in reference to wellconstruction as well as filter cake fundamental to protect the hole stability. Results,observations and conclusions were drawn upon using a case study comparing a well ononshore in Indonesia which had many drilling problems such as stuck pipe/differentialsticking and washouts/hole enlargement issues related to well bore stability, after using thewellbore stability agent, the problems that encountered significantly decrease.

The "U-Type" Wells History of Fuzzy Ball Drilling Fluids for CBM Drilling in China

The fuzzy ball drilling fluids have been developed on the basis of the circulation foam and Aphron to control lost circulation effectively. There are some difficulties in drilling U-type well, such as well-bore stability, cutting carrying problem, large torque and friction at the horizontal section, and formation damage to coal-bed. The objective of this paper was to show some applications of fuzzy ball drilling fluids on U-type wells of the Ordos Basin and prove the superiority of fuzzy ball drilling fluid in CBM drilling. To the three mentioned cases, the density of fuzzy ball drilling fluid was 0.90~1.18g/cm3, the funnel viscosity was 45~72s, the dynamic shear force was 12~19 Pa, the PV was 13~19mPa·s and the pH was ranged from 7 to 9. To use the fuzzy ball drilling fluids, the average ROP increased above 10% with no borehole complexity, such as stuck pipe, hole enlargement causing poor cleaning and etc. These cases reflected excellent properties of the fuzzy ball drilling fluids including effectively sealing, good carrying and suspension ability, formation damage control and compatible weighted by inert materials. Furthermore, the fuzzy ball drilling fluids will not affect BHA tools like motors and MWD in CBM drilling.

Wellbore Stability Analysis of Coal Seam Based on Hoek-Brown Criterion

Stable evaluation of coal strength is needed in coal well-bore stability analysis. The regular analysis method of wellbore stability adopts Mohr-Coulomb strength criteria to judge the collapse pressure. Coal is dual porosity structure and contains joint fissures richly. Hoek-Brown criterion is much more reasonable to estimate the strength of jointed and fractured rock. So Hoek-Brown criterion is used to analyze the stability of multi-lateral horizontal coal bed methane well. Considering the GSI (geological strength index), structural and surface conditions of coal, the coal and rock mass strength parameters are converted into the underground coal mechanical parameters based on the triaxial test of intact coal. According to the stress state of multi-lateral horizontal well, the borehole collapse formulas are established based on Hoek-Brown Criterion. The effects on the wellbore stability, due to the joint fissures of coal, borehole size, drilling disturbance, are also discussed in this paper.