RESEARCH PAPERS
Geolog is an active contributor to the technological advances in the mud logging field. This is achieved through its strong focus on R&D as well as its ongoing work with its clients, with whom it often works in conjunction to design, develop and evaluate new surface logging technologies.
Below are some of the research papers Geolog has written with its clients over the years:
1. Characterization of Conductive Fractures While Drilling
Agip/Geolog research paper prepared for presentation at the 1997 SPE European Formation Damage Conference
2. How To Improve Drilling Efficiency Using The Cutting Weighting Technology
ENI/Geolog research paper presented at the 2005 OMC fair.
Agip/Geolog research paper prepared for presentation at the 1997 SPE European Formation Damage Conference
When dealing with naturally fractured formations, the knowledge of the location and the permeability of the fractures intersecting the wellbore has a strong technical and economical impact upon drilling, production and reservoir management strategies. This paper presents a methodology which allows to perform a real time characterization of the conductive fractures intercepted by the bit while drilling. Such fractures are detected by monitoring continuously the mud losses at the rig-site using flow-meters measuring both the ingoing and the outgoing mud flow. The accuracy of such measurements is very high (mud losses as small as 20 liters can be monitored), and therefore also the smallest conductive fractures can be pinpointed.
A simple analytical model describing the mud invasion into a single fracture is used to invert the mud loss data in order to estimate the aperture and permeability of each fracture. This model has been validated with core measurements, and it is used in real time to perform a quick but sufficiently precise analysis.
The application of this technique to several field cases is also illustrated and discussed in terms of:
- Interpretation of the process of fracture plugging;
- Real time evaluation of the hydraulic aperture of the conductive fractures;
- Generation of a “secondary permeability log”.
Moreover some operative implications are discussed, such as:
- In the field of drilling, the muds, the lost circulation materials (LCM) and the cement plugs can be selected properly in order to avoid massive circulation losses and to minimize the damage due to mud invasion;
- In the field of production engineering, the completion schemes and the stimulation operations can be optimized through the knowledge of the most conductive intervals;
- In the field of reservoir engineering, a better modeling can be performed and a better exploitation of the naturally fractured reservoirs can be achieved.
Clients who wish to download the full research paper should request access by email to technology@geolog.itENI/Geolog research paper presented at the 2005 OMC fair.
Field Results following two years of joint field work between Geolog and the Italian Oil & Gas major ENI SpA.
To solve the serious problems experienced drilling deviated wells, ENI started experimenting with Geolog’s cutting weight sensors in 2003 (later to be named GeoCVM). One such device is installed in front of each shale shaker, and connected to the mud logging data acquisition system. Geolog’s real time engineering software transforms the weight of cuttings measured at the shale shakers into volume and the results are graphically displayed on the rig floor. Extensive field results confirm that the cutting weight sensors provide an accurate real time detection of cuttings volume taken out from the hole. This information correctly analyzed together with other drilling data, can be extremely useful to understand the different phenomena occurring while drilling. In particular the cuttings machine data are evaluated both versus depth and versus time in order to obtain the instantaneous picture of wellbore behaviour during drilling, tripping and circulating.
As a result, the drilling crew knows exactly what is happening downhole, e.g. when caving occurs or when cuttings remain in the hole and additional circulation is required. Furthermore, additional information is provided to the fluid engineer to better evaluate the mud efficiency.
The paper concludes that an accurate real time measurement of cuttings flow is essential to correctly evaluate the borehole behaviour while drilling, in combination with geomechanical borehole stability analysis and all other available drilling information and data.
A thorough, reliable, understanding of what is “really” happening downhole during drilling, tripping, allows the most appropriate operational decisions to be made, to:
- optimise drilling efficiency
- prevent getting stuck
- modify RIH and or POH procedures
- improve cementation when electrical logging caliper is not available to estimate cement volume.
- modify mud program and measure the effectiveness of the change.
The full research paper with case histories from wells drilled in the South of Italy is available to download by Geolog clients. Clients should request access by email to technology@geolog.it