What do you do if you encounter unexpected geological formations while drilling?

It′s common in deep wells with multiple folds to encounter layers that were not expected as seismic at that deep has poor resolution. If that is the case, STOP drilling and put the entire G&G team to work on it ASAP. A day or two of drilling rate (daily cost) is nothing in a deep well! Understand the situation and plan ahead. Of course if you know that multiple folding is possible, plan in advance during the planning phase in order to have tools or specialists ready to work on. Don′t be pushed by the guys saying put the rig to drill!

Here are some examples: - Evaluate the nature and extent of the unexpected formation to understand its potential impact on drilling operations. - Seek input from geologists, drilling engineers, and other relevant specialists to analyze the formation and determine the best course of action. - Modify drilling parameters such as speed, weight on bit, and drilling fluid properties to address the challenges posed by the unexpected formation. - Employ specialized drilling tools or equipment designed to handle challenging formations, such as PDC bits, diamond coring tools, or mud motors. - Have contingency plans in place to respond effectively to unexpected situations, including backup equipment, and alternative drilling strategies.

Absolutely, when encountering an unexpected geological formation during drilling operations, it's crucial to quickly assess the risk it poses to your operation. This assessment involves evaluating the formation's characteristics, including its hardness, porosity, and the presence of any fluids. Understanding these factors is essential for determining if the formation can potentially cause equipment damage, borehole instability, or safety hazards. Real-time data from logging-while-drilling (LWD) tools plays a vital role in effective risk assessment when encountering unexpected geological formations. LWD tools provide valuable information about the geological environment around the drill bit, allowing for real-time analysis and decision.

Based on the consistent review of geological map of the location to be drilled and offset wells, mud logging, MWD / MPD road maps are paramount. If unstable formation is encountered, drilling parameter will be adjusted to compensate for anomaly describing the subsurface condition. Proper drilling fluid properties / LCM are required to prevented formation instability while drilling.

when an unexpected geological formation is encountered while drilling, there is need to assess the risk associated to the operation by evaluating the formation samples taken from the shakers, like the cuttings size and shape, evaluate the porosity and permeability of the rock samples. observed the trend of broom stick and drilling parameters like WOB, rpm, ROP and current flow rate, the mud rheology and the LWD log in real-time. review the stratigraphic sequence and formation makers, observe mud pit and shakers,

Seeking the expertise of geologists or other subject matter experts when encountering formations beyond your expertise is a wise and proactive approach. These professionals can provide valuable insights into the nature of the formation and offer suggestions for appropriate drilling techniques or tools that can help navigate through it effectively. Collaborating with experts ensures that you're making informed decisions that enhance the safety and efficiency of your drilling operation. Their expertise can provide crucial guidance in addressing unforeseen geological challenges, ultimately contributing to the success of the drilling project.

One underutilized technology is using a PWD (pressure while drilling). For a mud engineer it has great uses. You can actually watch as any sweeps you pump pass through the bit & see in real time if it’s being effective in clearing any cutting beds that have formed.

If it’s a “wildcat” well, I recommend using a low lime lignosulfate water based mud. I find those are the easiest to adapt for any unexpected situation, regardless if it’s a kick, losses, or drilling into a contaminant.

Jim, you have nailed it. However, one really needs to be an expert mud engineer like you to handle the easiest mud system. With the passage of time, easierr things have become more difficult for current generation mud engineers because most of us are forgetting the basics of mud engineering, faster than we should. Therefore, my two Cent - Learn to speak to the well and understand its language! It conveys a lot when we listen, observe and understand.

Effective management of drilling fluids is essential when facing unforeseen geological formations, planning is thd key, keeping the mud system equipped with heavier mud for example to handle any unforeseen situation , and incorporating specialized additives, may be required to mitigate challenges like differential sticking and wellbore instability. Continuous monitoring and adjustment of fluid parameters are imperative to uphold ideal drilling conditions, using the real-time mentoring is a very effective tool as well.

It’s also important to realize that the offset data may be incorrect. For instance with drilling fluids, the previous data may have mud weights using a regular mud scale (balance) rather than a pressurized mud scale. If oil based mud was used, they may show the mud weight with the mud hot in the pits rather than the 80* F (26* C) that the API recommends to run the solids analysis at. Either of those items alone could mean a difference between taking a kick or losing returns.