Consultant wellsite geologists, in the oil and gas industry, provide contract services to clients by bringing skill and experience in different perspective of drilling and geology which allows the geology consultant to help companies identify and solve several different problems.
The Wellsite Geologist effectively supervise geological operations at the wellsite during drilling and acts on behalf of the operating oil company, reporting to the Operations Geologist. The role is also analytical in nature, with geological interpretations used to check that the well is meeting geological targets and also to advise drilling personnel on the geological causes of problems experienced during drilling as drilling equipment and fluids interact with the rocks forming the borehole wall. Early recognition of unpredictable geological anomalies can lead to rapid and cost-effective solutions being applied, making the well safer as well as within budget.
The wellsite geologist (WSG) and the company man (DSV), or drilling supervisor are usually the only oil producing company representatives at the rig. Both are oil company supervisors, but the geologist oversees a few teams while the company man supervises the entire drilling operation.
A Wellsite geologist is an oil company subsurface representative at well site or drilling location. They are involve in geological supervision at the well site
The basic function of wellsite geologist is to analyze drill cuttings obtain by mudloggers while drilling by identification and description of lithology with respect to depth which is an aspect of formation evaluation.
Wellsite geologist is often consultant who offer advice to the oil company and take some decisions in conjunction with the operation geologist at office in town. An example of this is when there is a need to stop drilling for casing or coring operation.
The geologist works under the supervision of operations geologists. They are located in the town offices and are the ones to whom wellsite geologist transmit all their report. Wellsite geologists are the main contact point between the oil rig and the geology and geophysics team in town. We communicate and discuss their intentions, plans and concerns to the teams at the wellsite.
What are the functions of wellsite geologist?
Wellsite geologist are responsible for well site geological supervision and all geological related activities at drilling site. The following are responsibilities of wellsite geologist:
Drill cuttings analysis and description
One of the basic duties is the identification and description of drill cuttings circulating out of the borehole with respect to depth. The description is often standardized and defined by each oil company. The wellsite geologist can classify the rock cuttings, check for evidence of borehole instability and confirm the presence of hydrocarbons. Drilling cuttings are analyzed and described using a stereoscopic microscope under white reflected light. To help identify the presence of hydrocarbons, a UV Box (Ultraviolet Box) is also used. Hydrocarbons will have a variable, but identifiable, brightness when exposed to ultraviolet light.
Several other tests are performed to carry out the formation evaluation. Such tests involve chemicals such as hydrochloric acid, to detect calcium carbonate content, and phenolphthalein, to detect the presence of cement and differentiate it from the formation.
Data correlations and decisions
The wellsite geologist analyses and interpret MWD/LWD data for confirmation of lithology, fluid type (oil, gas. water) and compare data gathered during drilling to prediction from seismic section and offset wells for determination of actual formation tops and reservoir sands to ensure the well is drilling in the formations forecasted for a given depth – deeper or shallower relative to the forecast?
When offset well data MWD/LWD and wireline logs are available to the wellsite geologist, data correlation can be carried out which can help to foresee important events like significant gas changes, drilling breaks and potential hazards which occurred in offset wells. You may find the older offset logs usually printed in paper or in a pdf format. The raw data is usually in a LAS file format, which is the most common for the mudloggers and LWD/MWD services to distribute.
Wellsite geologist need to advise the base office and drilling team on the best course of action in several scenarios. As the field geologist you have the responsibility of advising the team to either carry on or stop drilling. Nowadays this is usually a decision made together with operation geologist at office base in town. One such example is selecting at which depth drilling operations must stop in order to set casing or take a core sample.
Formation evaluation services team supervision
There are a few teams and services which wellsite geologists supervise. These are the mudlogging, MWD and LWD, wireline logging, core handling, micro and nano paleontologists. The geologist performs quality control and assurance of these services and the data they provide. These requirements can change from Oil Company to oil company.
The geologist is the key figure at the wellsite for taking decision with the office in town on when to stop normal drilling operations, as we approach coring point. Again, wellsite geologist need to use several correlations logs, drill cuttings , offset mudlogging, LWD data and other formation evaluation methods. When reaching coring point the drilling team starts to pull out of hole to proceed with the coring operation.
During coring operation, Wellsite geologist evaluates the few cuttings coming out of the wellbore while cutting the core. When the core is at surface, geologist take core chips from each meter (3 feet) of the entire core to evaluate the presence of hydrocarbons and to decide if coring operations should continue or stop in order to resume regular drilling operations (usually reaching the Total Depth). We must handle, or supervise the handling, of the core on surface ensuring proper markings and saw cutting as per oil company standards.
Casing point determination
The role of the geologist, for this operation, will be similar to the coring point approach as our main focus is analyzes of drill cuttings and correlating data with offset wells and ensure that there are no permeable / porous formations close to the bottom of the hole when we reach casing point, or in the rathole immediately below the casing shoe, as that increases substantially the risk of having losses during the cement job that will be performed after running the casing itself.
Geosteering and Horizontal drilling
Wellsite geologist (depending on the oil producing company) coordinate wellsite Geosteering operation in conjunction with Base Operation Geologist by analyzing and interpretation of real time data (Well inclination, Azimuth, correlation, Lithology, Biostratigraphy, reservoir porosity, formation dip and compare with the pre-drill geological model derived from seismic and offset Well data for decision-making as whether to increase inclination or to place the borehole trajectory higher in terms of TVD or to aim for a series of forward target points coordinates and to maintain direction/angle of inclination required at the bit when target is reached) while drilling horizontal Well.
Wellsite geologist have several reports to prepare daily, weekly, and at the end of the well. Some of the daily reports are the Daily Geological Report and the Lithology Log. These reports are updated with geological data, ongoing operations and important events.
There is also an End of Well Report or Final Well Report. This is produced and completed during the course of operations at the wellsite. They are delivered as updates to the operations and petroleum geologists during drilling operations. When drilling operations end these reports continue to be completed in the offices in town. They are updated until the end of all wellsite operations and only end when all the data from the entire well is obtained. Final completion of these reports will be carried out by the onshore geology team or the oilfield geologist, if asked to. There are several software packages available for us and these are usually provided by the oil company. Training on how to use them is one of the geological consultant’s responsibilities. For example, some of these software packages will allow you to produce the lithology logs, composite logs and other types of logs which may be required.
Safety and communication
HSE (Health, Safety and Environment) is a key aspect at the wellsite. The geologist is a leader and sets the example at all times encouraging others to work in safe conditions. Safety is one of the most important aspects of the entire operation.
Communication is also key to the success of the operations. Geologist communicate frequently with both the onshore office and the teams at the wellsite. This can reduce misunderstandings and mistakes. Make your teams feel comfortable enough to ask you anything in case of any doubts.
Talk to us for your upcoming wellsite geology consultancy requirement
We specialize in providing highly experience wellsite geologist to clients of all sizes in the oil and gas industry. Contact us at www.geodatadrilling.com Phone: +234 8037055441