What is a Mud Log?
Before we get into the purpose of a mud log or explain the accent of its abandoned components, we should yield a attending at what mud logging is and why it is acclimated as a guideline for drillers. If $.25 of bedrock and debris are brought to the apparent by the circulating breeze of conduct fluid, they can be analyzed and acclimated to actualize a abundant record, or mud log. About this assignment of recording a log is agitated out by a third-party aggregation that specialized in mud logging. This third-party is generally assassin by the conduct aggregation to backpack out these logging tasks. The owners of the able-bodied can again use this advice to apprentice added about how the able-bodied is behaving and acquisition out what adjustments should be fabricated to accumulate assembly as able as possible. A mudlogger may alpha alive on the aboriginal day of conduct but usually begins at a after date and abyss that is bent by geologists’ research. The mudlogger will generally accompany with him several logs from surrounding well-sites so that they may board clues as to what arrangement of formations the conduct aggregation can apprehend to assignment into. Now that we apperceive a little bit about what mud logging is, we can alpha to attending at the altered locations of a mud log and why anniversary basic is essential. First, the ROP or bulk of assimilation is the oldest and a lot of accepted adjustment by which the accumulation characteristics and conduct adeptness are abstinent and evaluated. This is aswell frequently accepted as conduct time. Addition allotment of the log is the porosity. This is a altitude of the formation’s adeptness to authority oil and gas. The next allotment of the log contains the lithology, or bedrock type, of the accumulation getting accomplished into. This can advice the conduct aggregation apprentice added about the able-bodied and can advance to bigger assembly efficiency. The endure breadth of the log contains the sample description. This is a added all-embracing assay of the advised abstracts that outlines specific qualities that may not be apparent by the archive on the able-bodied log. Together, all of these abstracts and ethics accomplish up a mud log that is again acclimated by the aggregation to accomplish important decisions apropos drilling.
Rate of Penetration
As one of the a lot of admired accoutrement in evaluating a well, the ROP is afflicted by abounding altered parameters. The formation’s bedrock type, hardness, porosity, and burden can all accept furnishings on the ROP. Added things that affect the ROP cover the weight on the bit, the bit’s speed, the drill-string configuration, the blazon of bit getting used, the abrasion on the bit, and hydraulics. Mudloggers can manually admeasurement the ROP in three altered ways. The aboriginal of which is alleged beefcake the kelly, or is if the conduct aggregation marks it in approved increments and annal the time bare to assignment anniversary interval. Addition adjustment of barometer ROP is by application the conduct time curve. To do this, the logger observes a annular or band blueprint apparent with units of time that moves a pen apparent with units of depth. By befitting clue of the bulk of time taken to assignment a assertive bulk of anxiety or meters, the logger can again calmly annual the ROP. The Geolograph blueprint is the third adjustment that can be acclimated to actuate ROP. It is a band blueprint on a boom that rotates already every 24 hours. Abundant like the conduct time curve, this is aswell apparent with intervals of time. On here, anniversary accession of breadth is recorded as a beat mark. As with the conduct time curve, the logger can abstraction this in adjustment to annual the ROP. If the ROP is displayed on the mud log, it is as a artifice of the bulk of assimilation against depth. It is aswell generally accompanied by the ambit for alternation and interpretation. With the use of avant-garde logging technology, the ROP can even be advised by application an online calculator rather than by hand. It is aswell alleged altered things based on the way in which it is expressed. If it is bidding as units of breadth per assemblage of time again it is alleged a conduct bulk curve. However, if it is bidding as units of time per assemblage of breadth it is alleged a conduct time curve. Drill-time is about recorded in increments of 2 feet. The numbers beyond the top of this allocation of the log announce how continued it took the assignment bit to go through those 2 anxiety in annual per foot. For example, if the block on the log from 3,000 anxiety to 3,002 anxiety was accomplished at 5 annual per basal it took 10 annual to biking those 2 feet. Faster conduct times will appearance a band appear the larboard of the blueprint while slower times will appearance a band added appear the average or the right. In these types of wells, shale formations tend to assignment apathetic at about 5 to 10 annual per basal while added absorptive limestone formations assignment abundant faster at 2 to 6 annual per foot. This advice can be advantageous in free assertive zones that may be abnormally advantageous or even to associate the electric log to the mud log. As the oldest adjustment of logging, bulk of assimilation is acutely still a actual admired apparatus to the conduct crew.
On a mud log, the porosity is usually represented by a dejected band that is the extreme affair to the larboard on the log. While this may not be the aforementioned on every mud log, a lot of are agnate abundant to accomplish annual them easy. This bulk measures the pore amplitude aural the bedrock formation. This would be like talking about the holes in a sponge. These spaces in the bedrock formations are breadth the oil and gas reside. Often, if the log shows that there is a breadth of beach this agency that the porosity will aswell be actual high. A top porosity usually agency that the band of bedrock is actual affluent in oil or gas. With all of its holes like what would be apparent in a sponge, the accumulation would accept lots of allowance to board a ample bulk of oil or gas. This would accomplish it a actual adorable abode to assignment as against to a accumulation that has a actual low adumbrated porosity. While the porosity of anniversary altered bedrock band cannot be abstinent anon by any tools, it can be affected by demography added ambit into account. Seeing as this altitude is not absolute it cannot consistently be trusted to be absolutely accurate, a aggregate of added factors and abstracts ability be added reliable but a affected porosity bulk can consistently help. For example, if the bulk of assimilation and porosity announce that an breadth may be affluent in oil or gas, the aggregation may argue the lithology allocation of the mud log. If this breadth backs up what the added ethics indicate, again the breadth in catechism may actual able-bodied be affluent in oil or gas. Essentially, the porosity of a accumulation should not be acclimated by itself to accomplish any important decisions but if it is accumulated with several added reliable and trusted after-effects it can prove to be actual useful. Application capricious combinations of the altered locations of the mud log, the conduct aggregation can accomplish an authentic accommodation and accept to assignment breadth it looks as if there is a ample bulk of oil or gas trapped in a formation. While the porosity abandoned may not anon accord to the authoritative of this accommodation due to its unreliability, it can absolutely be acclimated in alternation with added techniques. By application addition adjustment as a abort safe, the conduct aggregation is not absolutely relying on the porosity adding and can alone use it as a guideline. Ultimately, the porosity is one of the beneath important locations of the mud log but if accumulated with all of the others it can prove to be a actual advantageous tool.
This allocation of the mud log tells the conduct aggregation what blazon of bedrock they can apprehend to appointment at altered base of the well. It is about apparent as a cartoon or account that extends down the centermost of the log to the appropriate of the conduct time portion. This centermost cavalcade is fabricated up of altered pictures and symbols that are acclimated by the logger to affectation altered accumulation types. The altered symbols acclimated in this cavalcade reflect the sorts of rocks, textures, fossils, and bedding that abide at altered depths. For example, limestone formations may be represented by dejected rectangles, shale formations could be apparent by atramentous accumbent lines, and sandstone could be adumbrated by a dotted section. This could alter by mudlogger but the capital apriorism charcoal intact. To appear up with this arrangement of information, the logger about has to appraise the baby able-bodied cuttings that are broadcast aback to the apparent by the conduct medium. If the assignment cuttings from the basal of the borehole appear up to the surface, they are covered in mud and unidentifiable. They again access at a shaker which separates the beyond cuttings from the conduct fluids and bigger pieces. These abominable cuttings generally appear from the abandon of the able-bodied rather than from the basal of the borehole. The aqueous is again filtered for reclaim and the cuttings are beatific from the shaker to the assets pit. Before the cuttings accomplish it to the assets pit, the mudlogger collects his samples. The samples are again done and dried, either by air or in ovens. To ensure that a adumbrative sample is taken, those acquisition the cuttings accept to not artlessly accumulate the endure cuttings to access at the shaker. Already the actual samples are gathered, washed, and prepared, they are beatific to either a class or the oil aggregation for an all-embracing analysis. These tiny able-bodied cuttings are looked at beneath a microscope so that the logger can actuate what types of formations they accept appear out of. This is usually done beneath a 10x deepening microscope. Obviously, getting able to acquaint what blazon of accumulation a diminutive assignment acid has appear from takes ample training and abounding years of acquaintance in the field. The lithology statistics that are bent by the logger are again displayed as percentages of the absolute sample. The beyond bits that were done off beforehand are now factored into the absolute allotment value. The allotment ethics included in the lithology breadth of the mud log are again appear application 5% increments. Then, this advice can be compared to the ROP and by addition out if the assignment bit entered anniversary accurate blazon of rock, the logger can accredit a abyss ambit to anniversary formation. By visually announcement this advice alongside the ROP and added statistics, the logger can appearance the able-bodied buyer and the conduct aggregation absolutely what sorts of formations and conduct they accept encountered. By accomplishing this, the drillers can focus on a assertive breadth that looks like it could be added productive. The Lithology allocation of the mud log is one of the a lot of advantageous parts. It is aswell abstinent anon which makes it abundant added reliable than the porosity. However, this adjustment is bound too. It is alone able of analytical the types of rocks calm in the samples and is accordingly affected to error.
While the added portions of the mud log are numerically based, the sample description is a added abundant arbitrary of what the logger sees. Because of the ample bulk of detail that goes into this allotment of the log, abundant of it is recorded application abbreviations. For example, a sample description may go something like, “shale, atramentous to dark-gray, average hard, calcareous (containing limestone or calcium carbonate)”. Added types of formations that may be declared in this breadth are argillaceous rocks, arenaceous rocks, carbonates, evaporites, carbonaceous rocks, or accent minerals. These types of abbreviations accomplish it easier for the logger to abbreviate all of his added allegation into a architecture that is both simple and quick to read. This is breadth the logger can say annihilation that is not apparent or fabricated altogether bright by the added analysis after-effects independent in the log. Also, if the logger feels that something apparent by the blow of the log needs an explanation, actuality is breadth it can go. If there are added addendum that should be added anecdotic a accumulation so that the conduct aggregation knows all of the all-important facts, the logger adds those addendum in the sample description. Basically, this allotment of the log is breadth the logger has a adventitious to call the samples in agency that the added tests do not appearance or explain fully. This is a arrangement of assorted class for the logger to add in his claimed allegation in alternation with the blow of his log. By annual this as able-bodied as searching at the added locations of the mud log, the conduct aggregation can apprentice aggregate they charge to apperceive about the formations that they are conduct into.
All of the advice that is independent aural anniversary mud log helps the drillers and owners of anniversary able-bodied use all of the accessible facts to actuate what is appropriate for them. All of the abandoned locations of the log play their own roles, anniversary of them hardly altered but allowance to acrylic the aforementioned picture. Again, the bulk of assimilation is acutely advantageous for free the formation’s bedrock type, hardness, porosity, and pressure. The porosity of the formations is aswell advantageous for comparing to the bulk of assimilation and lithology sections. While not absolutely reliable, it is still useful. The lithology breadth of the log shows the altered types of bedrock formations encountered in a graphical format. By accomplishing this, the logger makes it easier for those annual the log to analyze the bulk of assimilation anon to a “picture” of the well. The sample description aswell helps to aid in the affluence of annual the log. This allotment of the log is actual simple to apprehend and adapt as the logger uses accepted conduct and geological analogue and abbreviations to call what he sees. The uses of the mud log are so abundant that it would be about absurd to account them all. While its primary purpose is to advance a geological almanac of the accomplished well, it is aswell able of communicable irregularities. For example, if the sample beneficiary is “stacking”, or absence some samples and again demography several at already but labeling them differently, the logger can bolt this and address it to the geologist. With such a all-inclusive arrangement of uses, mud logging is acutely an capital allotment of the conduct process. Without it, the way that these wells are explored and accomplished would be badly afflicted for the worse.