Latest News

A ghost from the past started hunting me when I went through my files. Ashamed of what I discovered I decided to tell everyone, especially young engineers, what not to do when setting a cement plug.

A few weeks back I was in the process of re-organizing my external hard drive. If you are like me, you have one of those external discs where you keep all your “work stuff.” My disc literally contains my entire professional life work.

Sometimes I am amazed by the stuff that pops-out when I search for something; exams from my early days as a drilling fluid engineer or as a cementer, CVs of candidates that I interviewed over a decade ago… you name it…

So, I decided to organize my hard drive with these objectives in mind:

• • To get rid of the stuff that does not help me anymore
  • To establish a structure that makes sense no matter where I work (or for whom!)
  • To find what I am looking for in the shortest time

One folder containing quite a few megabytes is labeled “Investigations.” There I keep lessons learned, technical and safety alerts and investigation reports from my former teams.

The folder sadly has documents from each and every single district I have worked.

A Safety instructor once told me, “company standards are written in blood.” Today I understand what he meant. Standards trail behind failures and accidents, and organizations and governments try to prevent their re-occurrence.

While organizing this folder, I realized that grouping the investigations by their topic instead of “by district” serves me far better in my current role as a well integrity “expert”.

Where the events took place is no longer relevant for me. The important thing is what those investigations addressed, so I can show young engineers how to deal with certain well situations, and how to prevent the occurrence of similar events.

Reading tip: Free water in Cement: Why is it critical?

When I focused on the investigations related to service delivery who had caused downtime or other types of “red money” (wasted money), the one ghost that chased me from everywhere I have worked was “The Failure of cement plugs”.

It is embarrassing how the reports reveal that the same mistakes are made over and over again in places as distant as Cabinda, Angola and Offshore Guyana, South America.

Free guide: The most common causes for leaks in oil wells and 8 questions to consider before you select solution.

To stop the feeling of shame, I will give you a quick summary of the more common causes of job failures when setting a cement plug:

1. 1. Length, insufficient cement slurry volume
      Operators that opt for saving money on slurry volume end up spending far more on rig time due to job repetitions. Plugs of less than 500 ft or less than 20 bbls of slurry are susceptible to fail.
   2. Slurry contamination due:
      1. 1. Inadequate base to set the plug
            Poor viscous pill design or no use of pills to support plugs placed off bottom. The density of the cement will force it to go downhole as shown in the picture below. Make sure you design a pill capable of supporting the slurry on top of it.
            
         2. Slurry contaminated during placement
            Fluids get intermixed when there are no physical barriers to separate them inside large drill pipes.
         3. Slurry jetting into the viscous pill
            The slurry, due to its weight, and assisted by gravity and the pump pressure, tend to jet into the viscous pill. Diversion in the annulus to force an upward flow is required to reduce the volume of slurry “lost” into the pill and on the bottom of the hole.
         4. Inadequate fluid displacement techniques
            Frictions in the wellbore caused by displacing fluids must exceed those of the fluids being displaced. That is why reviewing fluid properties is necessary. Hole geometry must be known to allow proper displacement. Sections of the hole with adequate size must be chosen to place the plug.
         5. Use of drill strings with large tool boxes that disturb the plug when the string is pulled out of the hole.
         6. Reversing too close to the top of the cement will cause contamination due to jetting of the displacement fluid into the cement matrix.
   3. Excessive slurry thickening time
      The longer the slurry remains fluid, the bigger the chances of the slurry getting contaminated.
   4. Poor quality control of slurry density before pumping
      Mostly due to the use of non-pressurized mud balances.
   5. No control of displacement volumes
      Due to the use of rig pumps or no use of cement truck displacement tanks.
   6. Inadequate waiting-on-cement times
      Anxious drillers that run and tag or attempt to drill out too soon.

The guidelines attached to this article (see also below) reveals more details on the reasons behind these failures and suggests how you ensure a successful cement job.

If you follow them, I am certain that your chances of getting it right the first time will increase significantly.

Best of Luck!

Posted by Miguel Diaz

Miguel has 20 years’ experience from operations, technical advisor, quality assurance, business development and management positions in the oil & gas industry from all areas of the high-pressure pumping services. He has worked in South America, the Caribbean Sea, central and eastern Europe, Sub-Sahara Africa and the middle east. Miguel serves as one of our cementing experts and is our Business Development Manager for the Middle East and North Africa region.

This article was sourced from Wellcem: https://blog.wellcem.com/cement-plugs-a-routine-or-a-nightmare

For more information from Wellcem you can see their blog here: https://blog.wellcem.com

There are different definitions of Well Integrity. The most widely accepted definition is given by NORSOK D-010:

“Application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well”.

Another accepted definition is given by ISO TS 16530-2:

“Containment and the prevention of the escape of fluids (i.e. liquids or gases) to subterranean formations or surface’’.

Well Integrity is undoubtedly a multidisciplinary approach. Therefore, well integrity engineers need to interact constantly with different disciplines (e.g. well intervention and drilling) to assess the status of well barriers and well barrier envelopes at all times.

Introduction

The Middle East offshore market generally has shallow water depth operations in high salinity water environments. As fields in the Arabia Peninsula mature and production declines they need extensive recovery enhancement and workovers which place added stress on the asset. In conjunction with the age and salinity of the water these works can effect the structural integrity of aging wells. This forces further works to take place, including diagnostic runs and tubing remediation.

In the Middle East companies including Saudi Aramco, QP, Zadco and ADMA-OPCO have become experts in dealing with mature offshore wellstock, and below is a case study from the region highlighting the best practice that has been learnt.

Middle East Experience of Aging Well Stock Management

With a global slowing of drilling activities, we are often finding ourselves working over mature fields with old well stock to encourage greater recovery volumes and meet the demand for hydrocarbons. Mature assets have unpredictable behaviors, and this demands highly skilled teams and well thought out intervention activities to ensure the continued production of these assets. >Case One: The Well

In one example the Middle East operator observed live wells having fluid mobility into annulus space, resulting in the bleeding of hydrocarbons at the surface. The Annulus-B pressures were reaching 1000psi, and there was clear evidence of communication within casings. The hydro-testing of annulus space showed the wells were unable to withstand the test pressures, so ultrasonic testing, cement bond logging, and other logging techniques were used to quantify the integrity and accurately identify leak paths ahead of restoring the well integrity of failed Annulus-B wells. It was decided to repair the conductor pipe and perform casing patches externally and internally and cement consolidated rock formations, then cover with a tie back. As a remediation strategy, a cement barrier was placed in production casing above the reservoir using sleeves, patches, perforating two-zone techniques and milling to mention a few.

The utilization of section milling as a remediation measure is interesting. Its effectiveness was later verified with cement bond logging to ensure that integrity was assured. The operational challenge faced from leveraging milling technology was a failure to pass the bottom of section mill cut. This was then solved by using a taper mill to drill the required section.

The root cause of the integrity issues were understood to be generic aging (the wells were approximately thirty-years old), poor cement jobs and the possibility of ineffective drilling practices used at the initial stages of the well’s life. The core objective was to restore to well integrity of production and injection wells and rule out well abandonment as an option. This was achieved and the programme was a success – resulting in the extension of the mature asset’s life.

Case Two: The Conductor

In this case the operator discusses two fields in the Arabian Peninsula, one consisting of 99 wellhead towers, and the other having 116 wellheads towers – cumulatively the integrity department is having to manage 217 wellhead towers. The technical challenge faced by the operator is that over 60% of these wellheads towers are in life extension phase.

If offshore conductors corrode to the point their structural integrity fails, they are bound to buckle leading X-mas tree and other related critical equipment to fail.

The wellhead towers are typically 3-legged and 4-legged (with 9 slots) having above water guide support and near seabed conductor support. One of the main issues the operator is facing is having 9 slots conductor’s exposure to the huge amount of wave load which may transfer through conductor guides followed by jackets to piles. It is important to highlight conductor guides support for the wellhead towers is necessary, otherwise, the conductor will be free standing and may subject to vortex induced vibrations which could fail under free vibration or due to fatigue.

When designing conductor supports it is essential that the weight from X-mass tree, BOP, lateral support, vortex induced vibration, corrosion protection and marine growth should be considered among other requirements with respecting code and standards established by NORSOK, API, and ISO.

In the region operators have typical well conductor loading depth varying from 100ft to 300ft, having two types of loadings axial compression and global bending. The operational integrity is assured by conducting scheduled screen inspection (visual inspection) followed by detailed inspection using Saturated Low-Frequency Eddy Current (SLOFEC) and Pulsed Eddy Current (PEC) quantifying the minimum wall thickness, external and internal detections, separate mapping and other techniques.

By executing these inspections and then coupling them quickly with remedial works, abnormalities in the aging conductor were identified and rectified within the scheduled inspection window. In one example it was discovered there was at least a minimum wall thickness and therefore efficient strength to assure the stability of the asset against atmospheric, splash and full submerged segments of the conductor – and therefore its ability to cope with the stress of a work over for production enhancement applications was established.

The results of applying this conductor programme across the two fields showed that a robust remedial strategy, as emphasized by this operator, reduced rig intervention for replacement and fewer rig repair strategies such as reinforced cement, bolted clamps and welded sleeves just to mention a few.

Conclusion

Well integrity is becoming increasingly important in maturing fields in the Middle East. The asset integrity lifecycle is ever evolving, and lessons learned must be added to our codes of practice and become ‘the norm’ for future projects. This will ensure that collectively we are able to continue the efficient production from our existing assets for the benefit of future generations.

The insights captured in this document are indicative of a culture where we need a continuous improvement across training our personnel to increase competency, safety and cost-effectiveness of operations and use innovative approaches in low price environment.

From these examples, a scheduled approach to preventative maintenance workovers are shown to be more cost-effective overtime rather than dealing with sever and critical integrity works which are bound to follow.

Gain insight into the growing Integrated Well Services Market in the Asia Pacific in this bespoke report by Offshore Network

Access a detailed well intervention case study that utilised cutting-edge rigless, riserless technology. See the full report from Sapura Energy which covers the Browse Basin project that took place offshore Australia.

By Mark Plummer MSc BEng

Stuart Wright Pte Ltd’s (SW) CEO, Colin Stuart, and Well Engineer, Mark Plummer recently completed a one-year project supporting the Department of Natural Resources Mines & Energy (DNRME) in Queensland, Brisbane to perform a Well Programme Assurance Design and Construction Review (WEPA DCR) for high risk and complex wells.

The objectives of the WEPA DCR were to understand, by observation, how operators are meeting the relevant statutory provisions in the legislation; including subsidiary mandatory safety requirements, the Queensland Code of Practice and recognised industry standards.  Consistent with the Queensland government policy, the Inspectorate is collaborating with the industry to promote the safety and technical standards for petroleum and gas operations.

Following consultation and dialogue with industry, seven (7) Operators were selected as suitable candidates for the well programme assurance review. The programme was conducted in three stages as outlined in Figure 1 below.

Figure 1 – WEPA Design & Construction Review Process

WEPA Stage 1 – Understand with the petroleum operator, their well design protocols and standards, and agree specific well selection;

WEPA Stage 2 – Engage in well design and planning process of the selected well programmes; and finally; and

WEPA Stage 3 – Oversee well construction against the plan in the well execution stage. In particular to carry out well barrier monitoring and validation using SW’s proprietary Right Time Barrier Condition (RTBC) well barrier monitoring system.

Well Design Phase Review Methodology

Through discussion between the Regulator and each individual Operator, eight (8) suitable candidate wells were identified for the Well Programme Assurance review. Subsequently, a copy of Operator standards and well specific documents (e.g. Well Basis of Design, Drilling Programme, Drilling Fluids Programme, Cementing Programme, Casing and Tubing Design, Well Barrier Programme) were provided by the Operator for review by Well Inspectors.

The design phase review methodology was as follows:

1. Tenure holders informed DNRME of the commencement of well design and provided relevant corporation documents/standards to DNRME.
2. Inspector(s) from DNRME reviewed operator documents/standards and identified that they comply with mandatory regulatory requirements or noted any gaps.
3. Inspector(s) from DNRME reviewed the well specific programme including ‘well basis of design’, ‘drilling fluid programme’, ‘casing & tubing design report’, ‘well barrier programme’ and ‘cementing programme’ to confirm if these documents were compliant with mandatory regulatory requirements and good industry practice.
4. DNRME raised any clarifications arising from the standards and well design review with the Operator via a clarification register.
5. DNRME provided a summary report containing any apparent non-conformance items for discussion with the Operator.

Well Construction Phase Review Methodology

Stuart Wright’s proprietary well barrier monitoring and validation system, RTBC, was used by DNRME to monitor drilling operations for selected wells. This exercise was the final stage for a given selected well, in DNRME’s WEPA DCR programme.

The system was used to assess each well for compliance, with their own standards and mandatory regulatory requirements. Specific barrier acceptance criteria were created in RTBC, which were extracted from Operator standards, the drilling programme and relevant legislation. Each barrier element during well construction was then assessed for reported validation, and assigned a traffic light colour (red, amber, green) rating depending on the result of the rating.

RTBC creates a Daily Integrity Report (DIR) capturing the barrier validation result.

The process of assessing compliance during well construction was as follows:

1. DNRME set up a specific Barrier policy library for each Operator in RTBC

1. DNRME set up a Well Barrier Plan based on the drilling programme, capturing all well construction activities and planned barrier validations
2. DNRME received DDRs and other daily reports from the Operator from well spud until suspension/abandonment
3. DNRME reviewed the operations stated in the Daily Drilling Reports (DDRs) and other daily reports and updated the barrier conditions and as-built diagrams in RTBC
4. A Daily Integrity Report (DIR) was created for each day of operations for internal DNRME review before distributing to the Operator (see Figures 2A and 2B below). Any apparent gaps or discrepancies were discussed directly with the appointed Operator personnel

Figure 2A – Example Daily Integrity Report (Pg.1) – sent to Operator on a Daily Basis

Figure 2B – Example Daily Integrity Report (Pg.2) – sent to Operator on a Daily Basis

Key Findings

A range of useful findings arose from the WEPA study and, in particular, the use of RTBC to track barrier validation during well construction provided close monitoring and feedback which was beneficial to both the Regulator and Operator:

KF #1 – In general, the Operator standards compliance with mandatory regulatory requirements was good, but with individual exceptions which were fed back to Operators and improvement processes agreed.

KF #2 – Maintaining an overbalance margin to the bottom hole pressure (BHP) is a critical barrier during well construction. Operator standards for petroleum wells reviewed by DNRME could be further enhanced by stipulating a minimum overbalance to BHP requirement. 

KF #3 – Several Operators did not achieve regulatory compliance with the minimum 70% standoff for casing centralisation in their well design. The primary reason cited for this non-compliance was that the centralisation modeling simulation called for large sections of the casing having 2 centralisers per joint to achieve the required 70% standoff and Operators opined that the risks associated with running this many centralisers outweighs the benefit.

KF #4 – During the WEPA study, DNRME noted that the Operator’s design and planning process was often completed very late and, in many cases, only a few days prior to well spud which has an impact on risk during the well construction phase.

KF #5 – 75% of the gas-producing petroleum wells reviewed during the WEPA study were designed with standard Buttress Thread Connections (BTC) or Long Thread Connections (LTC) in the production casing string, which is common practice, deemed to be adequate as reservoir pressures were less than 3,000 psi.  For gas-producing petroleum wells, the selection of premium (gas-tight) connections would help to mitigate, over time, the risk of a leak path for hydrocarbon gas into the B-Annulus with associated consequences, though DNRME accepted that current industry standards support the common practice and the risk assessment approach currently used is valid.

KF #6 – The use of a barrier monitoring system demonstrated that Operators could not, in a limited number of cases, show compliance in all respects with their own standards and regulatory requirements during well construction given the conventions and format of the standard DDR reporting process. The Inspectorate had to review documents and data other than the DDR to complete the barrier validation picture.

KF #7 – The integrity reporting system used (RTBC) did give regulator and operator insight into escalating compliance risks. Furthermore, it allowed the Inspectorate to demonstrate in the captured database, a record that the operator is in compliance with regulation OR where they are not, it is transparent, and a flag raised.

KF #8 – The Daily Drilling Reports (DDR) focus is typically around performance and Occupational Health and Safety (OHS). However, no clear picture emerges in a typical DDR of an equal focus on well integrity and specifically loss of control risk.

Preliminary Conclusions of the WEPA Study

The findings and preliminary conclusions of the WEPA study were presented, on behalf of DNRME, by Colin Stuart at the Oil & Gas UK “Safety 30 – Piper Alpha Legacy: Securing a Safer Future” conference which was held in Aberdeen in June, 2018. A summary of the preliminary conclusions of the WEPA study is detailed below:

1. There was some evidence of failure to follow approved plans during execution, particularly when problems developed. Management of Change (MOC) documents did not tell the complete picture.
2. The use of a Daily Integrity system approach created transparency when deviations occurred, and forced better management response.
3. The WEPA programme showed potential to reduce risk through better well integrity transparency. This could be achieved, as demonstrated, through the use of RTBC to properly identify Controls, assess that these have been Validated and record the Evidence of validation using a modern cloud-based data storage solution, which ensures data availability and instant retrieval and analysis.
4. The WEPA process has important implications for Oil and Gas wells but also emerging Geothermal well projects where, due to the current absence of global standards, compliance challenges exist.
5. The WEPA approach could be deployed across several international regulators to create a limited but global barrier validation best practice and potential failure databasefor well construction, including all critical component failures affecting well integrity.

This project summary has been approved by DNRME.

Understand how the Completions Standardization Technical Committee (COMSTEC), comprised of members from Petronas MPM and regional operators and service companies are tackling three main operational inefficiencies: Packers, safety and flow valves and operational procedure.

In this article, we review the situation and prospects for the offshore well intervention market, with comment on best practice, based on a presentation at OWI APAC 2018 (Kuala Lumpur) by Dan Cole, McKinsey & Company.

SIA Cyclit Konsultants:

Pilipishin B., PhD,

Havenson I., PhD, Gonca V., PhD, Brushtunov V., PhD, Huk I.

Our original method of prediction hydrocarbon traps is based on the theory of sedimentary cyclicity (lithmology) and on the assumption of discompaction and compaction zones: oil or gas field is formed by hydrocarbon migration from the source of their generation and the subsequent accumulation and conservation in the traps, which are located along the ways of migration.

The method can significantly improve the efficiency of geological exploration work in all their phases and stages. One of the main feature of our method is that we definitely prove where wells SHOULD NOT BE PROJECTED. It will RADICALLY REDUCE fields’ research and exploration costs.

For last 20 years we analyzed more than 50 deposits (mainly Ukraine and Khazahstan) with really positive results: overall average probability of successful wells is more than 70%.

The “Seismocyclit” group carries out processing of customer’s geophysical data and search for oil and gas pools, using its own exclusive methodology. The proposed methodology includes original methods of processing and interpretation of geophysical data, realized in form of programme-methodical complexes (PMC) “Seismocyclit” and “AFCM” (amplitude-frequency characteristic of medium).

It allows:

– To carry out construction of stacks with improved signal-to-noise ratio, eliminating regular and irregular unwanted signals, which do not respond to the principle of reciprocity in seismic survey.

– To accomplish stratigraphic identification of the reflecting horizons, using logs in form of cyclites.

– To discover structural features of the geological section, and ways of migration – hydrocarbon delivery channels, which often coincide with tectonic failures.

– To single out zones, where reservoirs and impermeable beds are developed. For these goals, the sections of “AFCM” (amplitude-frequency characteristic of medium) are used, which are characterized by important and distinctive feature: the calculation of colour instead of it’s assignment. Changing of the colour on the “AFCM” sections shows that the reservoir characteristics of the section change. In the given variant of calculation, horizons of the reservoirs are displayed on the “AFCM” sections in dark blue and black colour. The efficiency of this methodology is proven on a number of structures and fields connected to various types of sections. On the presented “AFCM” sections, four boreholes (red colour) are shown, which were drilled with the help of our recommendations and have given the production in terrigenous section.

These programme-methodical complexes (PMC) “Seismocyclit” and “AFCM” – amplitude-frequency characteristic of medium have been effectively used for prognosing traps in Upper Jurassic carbonate section of Precarpathian deep.

On the “AFCM” section in the upraised block of Upper Jurassic deposits, the extensive zone of reservoirs development can be pointed out, whose presence is proven by the results of boreholes testing. In the upraised part of the sinked block we can point out similar zone which is prospective.

– Additionally for prognosing the presence of hydrocarbons in trap the data of electrical prospecting can be used – it may help to calculate longitudinal electrical resistance on several deep levels. The existence of structural form and higher resistance on certain stratigraphic levels can indicate hydrocarbons’ presence in the structure.

The proposed methodology of hydrocarbon pools forecasting can be used at any stage of geological prospecting works, significantly raising their efficiency.

The following input data are necessary for our job:

• • data of the 2D or 3D seismic survey;
  • log diagrams of acoustic and (or) gamma-ray logging of the wells;
  • a priori geological information on the geological structure of the investigated area.

As the result of the works the Customer will obtain the following main materials:

1. 1. At the prospecting of the new hydrocarbon fields:
      • • conclusions as to the expediency of drilling the wildcats and the indication of their location and the expected bedding depths of the producing layers;
        • scheme of disposition of the detailing seismic profiles with the recommendations as to the methods of the field works carrying out.
   2. At the exploration of producing hydrocarbon fields:
      • • prognosing maps of the hydrocarbon pools in the definite interval of the depths;
        • conclusions as to the presence of new objects of the prospecting in the field;
        • recommendations as to the exploration works carrying out in the field with the indication of the location of new exploratory wells.