The report is about PDO to obtain the raw data besides acquiring the relative temperature data.sssssssssssssssssssssssss

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Two tests were performed on SAR-1, the first was carried out in September 1998 and the second in May 2014. SAR-1 was drilled from 3651 to 3790 mahbdf.  At the expiry of the four-day flow period, a regular drop in the rate of dry oil was observed and this was recorded from 300 m3/d to 240 m3/d. The oil gravity was observed as 33.4 API and the ratio of gas-oil was 230 m3/m3. The FTHP became steady and constant, i.e., 16,000 kPa during the end of the flow period. For 5 days, a PBU (pressure build-up) survey has been conducted and the well was shut-in at surface. A production log and surface PVT samples were taken afterwards (Ref. Sarmad A3C 2013 FSN). 


Till the execution of development and appraisal plan, a deep set plug was employed in the tubing to defer and push back the SAR-1. From wells SAR-3, 4 and 6, first production was started in February 2013 by the Sarmad A3C reservoir.  For evaluating the limestone interval, a second test was carried out in May 2014 (whereby the perforation was between 3725 and 3760 mahbdf). SAR-4 and 6 are the adjoining wells, which were operational during the course of this test.  The scientists examined the collection period to identify any interference from the adjacent two wells.  On limestone interval, the findings from the second test were discussed by this NFF.


1.            QAQC & GUAGE CORRECTION:

Two downhole memory gauges (SPARTEK 1169 F5) were employed to obtain the raw data besides acquiring the relative temperature data. For pressure correction, the scientists used a fluid gradient of 7.3 kPa/m (static oil column) by applying PVT data.

The comparable readings were observed from the two gauge data and their relationship.  Further investigations can be carried out by using the readings from the bottom gauge.


However, the oil rate readings and the pressure readings were a slight different from each other. Once the well was shut-in for the main build-up, the group waited for 3 hours and then took the first oil rate measurement, which would most probably result in some ambiguity in the subsequent analysis.  Scientists introduced two possible corrections for addressing the mismatch issue. In the first approach, the rate was inferred to initial rate before shut-in by a straight decline.  The adjusted oil rate is then demonstrated by the plot mentioned as under.



During SAR-1 testing, both the adjacent wells, i.e., SAR-4 and 6 were functional as already discussed. There was no declining trend in pressure observed at SAR-1, which indicates that either SAR-1 is restrained within its fault block to a certain extent or the pressure boundary of the other wells had not been navigated / crossed by the transient.


1.            RESULTS & ANALYSIS:

With a circle boundary model, the group achieved the ideal matches through homogenous reservoir by implementing the techniques to select the suitable model, e.g. system recognition and flow regimes from the diagnostic plot of log-log. Nonetheless, a slight difference was observed in the results, since two different methods were used in correcting the mismatch between the rate and pressure readings.


At the start of the derivative response, a normal horizontal line is shown by the log-log plot, when the group was considering the flat rate reading. A sharp plummet was observed in the derivative response after that. A constant pressure boundary can be a reason of this drop / plummet.


The skin and wellbore storage are likely to administer the early time response (well response) in SAR-1. 

The derivative had a sharp downwards movement in SAR-1 PTA. A constant pressure boundary could most probably be the reason of this movement / action.


Moreover, the derivative response was matched by two models; one was having circle boundary and the other one was without boundary. The homogenous reservoir with a circle boundary model has been selected and referred to as the base case model. Table 4 encapsulates the results of the two models.


We received almost the old and similar results, while applying the decline rate method in place of a flat oil rate to correct the mismatch. In general, the results are unresponsive to the decided methodology as far as this particular test is concerned.  Applying the adjustment is the most important task so the first oil production and the pressure drawdown could be aligned with each other. 


The mPLT indicates that the top 4.4 m of the interval delivers the most flow contribution.  The scientists introduced another model to match the derivative response for confirmation. A two layer reservoir having a circle boundary is supposed by this model.  However, the group remained unable to achieve the desirable match.

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