Weight & Cost estimation application Ciesta

In brief

Ciesta is a software application developed by Citec for weight and cost estimates for offshore fields.

Why Ciesta?

The current low oil prices put increasing pressure on future investments in oil and gas fields. Profitable investments require better estimates of projects in early phases. There is also an increasing need to analyse a larger set of project design combinations. Ciesta is a software application for weight and cost estimates for offshore fields designed to meet these demands. It aims to produce complete and reliable estimates for small and large projects based on minimal information such as daily production of oil, condensate and gas. Ciesta may also be used to produce estimates when more information about the project is available, it can thus be utilized at different stages of the project development.

Ciesta also allows the estimator to select different main functions for a specific topside, thereby facilitating analysis of a broad set of possible project configurations. These main functions may be various production, accommodation, on board power production or full or partly drilling. Ciesta also produce estimates for other field components such as subsea installations.

Topside estimates based on historical data

Estimates in Ciesta are based on a huge database of historical data/information. These data may be applied by an experienced estimator in order to select the best data foundation for an estimate. The data items' relevance may differ from estimate to estimate based on the configuration of a specific project. Ciesta therefore allows the estimator to select a set of historical data items that is best suited for the project in question. This is done through extensive use of graphical presentations of weight and cost historical data items for estimates at different levels (e.g. discipline bulk weights or man-hours estimates for engineering of e.g. piping in one defined contract/module). This graphical presentation allows the estimator to detect trends in the underlying historical data set as well as selecting the most relevant set of historical data items. 

Fig 1_Selection_Graph_cropped.png

Fig 1. Selection graph


What constitutes a relevant set of data items must be based on the estimator's professional judgements. Ciesta is therefore not a black box producing estimates beyond the estimators' control.  On the contrary, Ciesta aims to make optimal use of the estimator's professional competence and experience. Transparency, control and documentation of estimates are therefore top priorities in Ciesta. These criteria guarantee optimal reliability of the estimates. Ciesta also maximises re-use of sets of historical data items since they may be copied from one project combination to another.


Ciesta is based on modularization. This means that every estimate consists of a combination of several building blocks. These building blocks may occur in different combinations in different projects. Ciesta therefore allows for efficient estimation of a large number of different topside configuration by modifying these combinations.

Risk analysis

Ciesta also produce risk analysis for aggregated weight and cost estimates. This is done by using a Monte Carlo simulation technique based on variations in the applied historical data items. Since the risk spread is assessed by using historical data the risk analysis will have an empirical foundation rather than subjective assessments from expert panels. The risk analysis will give the estimator references for assessing expected values and allowances based on a Gaussian probability distribution (normal distribution). Other probability distributions such as triangular, beta and lognormal distributions are also available.

Fig 2_Probability_Distribution.png

Fig 2. Probability distribution 


By using standardized sets of historical data items, Ciesta also allows for complete and reliable benchmarking of estimates. Benchmarking is done by presenting graphs on different levels showing how an estimated project would compare to as-build projects. Such graphs (e.g. total bulk weight against production measured in tonnes of oil equivalents) show immediately whether an estimated project stands out in any way compared to as-build projects or whether it has mainstream attributes on critical factors. Ciesta allows the estimator to select among a multitude of benchmark criteria (e.g. weight and cost against different production capacities) in order to produce complete and consistent benchmarking of estimated projects.

Equipment List Generator (ELG)

Ciesta can dimension the central equipment of the topside using a comprehensive set of algorithms based on common process methodology. Relatively few basic design parameters are needed, like expected flowrates, inlet pressure, temperature, sparing philosophy (1x100, 3x50, etc.), number of separation stages etc. The results can be exported to give a head start in the establishment of the Master Equipment List for the project. The calculation also results in a set of equipment weights, which is used as basis for further estimation of the topside. A change in the fundamental design parameters will cause recalculations throughout the estimation process giving an immediate result in weight and cost for the total topside. This unique feature is valuable when evaluating sensitivities.

Making optimal use of estimators

Estimation can never be a fully automated process; the estimator will always be the critical success factor. We aspire to automate repetitive tasks like selecting and manipulating data whenever it is possible, so that the estimators are allowed to focus on important design questions. Estimate quality will therefore be greatly enhanced. This is exactly what Ciesta is designed for.

Field development cost analysis

The central feature of Ciesta is the excellent topside weight and cost estimation tool. However, our systems cover all parts of a field development. Citec can estimate CAPEX of greenfield topsides, brownfield topside work, substructures and subsea developments including SPS and SURF scope. The goal is to cover all economical aspects of any field development including estimates for OPEX and production revenue. This enables us to evaluate the total economic picture of a field development. 

The quality of weight and cost estimates will be a critical factor when investments profitability is under increased pressure. Investors will need to have unquestioned confidence in such estimates in order to have a realistic view of expected future profits. Ciesta is a tool which can provide this confidence and thus give investors an optimal assessment of their project's financial sustainability.